AllegroGL will automatically load the following extensions:

ARB Extensions:
GL_ARB_multitexture 
GLX_ARB_get_proc_address 
GL_ARB_transpose_matrix 
WGL_ARB_buffer_region 
GL_ARB_multisample 
GL_ARB_texture_env_add 
GL_ARB_texture_cube_map 
WGL_ARB_extensions_string 
WGL_ARB_pixel_format 
WGL_ARB_make_current_read 
WGL_ARB_pbuffer 
GL_ARB_texture_compression 
GL_ARB_texture_border_clamp 
GL_ARB_point_parameters 
GL_ARB_vertex_blend 
GL_ARB_matrix_palette 
GL_ARB_texture_env_combine 
GL_ARB_texture_env_crossbar 
GL_ARB_texture_env_dot3 
WGL_ARB_render_texture 
GL_ARB_texture_mirrored_repeat 
GL_ARB_depth_texture 
GL_ARB_shadow 
GL_ARB_shadow_ambient 
GL_ARB_window_pos 
GL_ARB_vertex_program 
GL_ARB_fragment_program 
GL_ARB_vertex_buffer_object 
GL_ARB_occlusion_query 
GL_ARB_shader_objects 
GL_ARB_vertex_shader 
GL_ARB_fragment_shader 
GL_ARB_shading_language_100 
GL_ARB_texture_non_power_of_two 
GL_ARB_point_sprite 
GL_ARB_fragment_program_shadow
GL_ARB_draw_buffers
GL_ARB_texture_rectangle
GL_ARB_color_buffer_float
GL_ARB_half_float_pixel
GL_ARB_texture_float
GL_ARB_pixel_buffer_object 

Non-ARB Extensions:
GL_EXT_abgr 
GL_EXT_blend_color 
GL_EXT_polygon_offset 
GL_EXT_texture 
GL_EXT_texture3D 
GL_SGIS_texture_filter4 
GL_EXT_subtexture 
GL_EXT_copy_texture 
GL_EXT_histogram 
GL_EXT_convolution 
GL_SGI_color_matrix 
GL_SGI_color_table 
GL_SGIS_pixel_texture 
GL_SGIX_pixel_texture 
GL_SGIS_texture4D 
GL_SGI_texture_color_table 
GL_EXT_cmyka 
GL_EXT_texture_object 
GL_SGIS_detail_texture 
GL_SGIS_sharpen_texture 
GL_EXT_packed_pixels 
GL_SGIS_texture_lod 
GL_SGIS_multisample 
GL_EXT_rescale_normal 
GLX_EXT_visual_info 
GL_EXT_vertex_array 
GL_EXT_misc_attribute 
GL_SGIS_generate_mipmap 
GL_SGIX_clipmap 
GL_SGIX_shadow 
GL_SGIS_texture_edge_clamp 
GL_SGIS_texture_border_clamp 
GL_EXT_blend_minmax 
GL_EXT_blend_subtract 
GL_EXT_blend_logic_op 
GLX_SGI_swap_control 
GLX_SGI_video_sync 
GLX_SGI_make_current_read 
GLX_SGIX_video_source 
GLX_EXT_visual_rating 
GL_SGIX_interlace 
GLX_EXT_import_context 
GLX_SGIX_fbconfig 
GLX_SGIX_pbuffer 
GL_SGIS_texture_select 
GL_SGIX_sprite 
GL_SGIX_texture_multi_buffer 
GL_EXT_point_parameters 
GL_SGIX_instruments 
GL_SGIX_texture_scale_bias 
GL_SGIX_framezoom 
GL_SGIX_tag_sample_buffer 
GL_SGIX_reference_plane 
GL_SGIX_flush_raster 
GLX_SGI_cushion 
GL_SGIX_depth_texture 
GL_SGIS_fog_function 
GL_SGIX_fog_offset 
GL_HP_image_transform 
GL_HP_convolution_border_modes 
GL_SGIX_texture_add_env 
GL_EXT_color_subtable 
GL_PGI_vertex_hints 
GL_PGI_misc_hints 
GL_EXT_paletted_texture 
GL_EXT_clip_volume_hint 
GL_SGIX_list_priority 
GL_SGIX_ir_instrument1 
GLX_SGIX_video_resize 
GL_SGIX_texture_lod_bias 
GLX_SGIX_dm_buffer 
GL_SGIX_shadow_ambient 
GLX_SGIX_swap_group 
GLX_SGIX_swap_barrier 
GL_EXT_index_texture 
GL_EXT_index_material 
GL_EXT_index_func 
GL_EXT_index_array_formats 
GL_EXT_compiled_vertex_array 
GL_EXT_cull_vertex 
GL_SGIX_ycrcb 
GL_EXT_fragment_lighting 
GL_IBM_rasterpos_clip 
GL_HP_texture_lighting 
GL_EXT_draw_range_elements 
GL_WIN_phong_shading 
GL_WIN_specular_fog 
GLX_SGIS_color_range 
GL_EXT_light_texture 
GL_SGIX_blend_alpha_minmax 
GL_EXT_scene_marker 
GL_SGIX_pixel_texture_bits 
GL_EXT_bgra 
GL_SGIX_async 
GL_SGIX_async_pixel 
GL_SGIX_async_histogram 
GL_INTEL_texture_scissor 
GL_INTEL_parallel_arrays 
GL_HP_occlusion_test 
GL_EXT_pixel_transform 
GL_EXT_pixel_transform_color_table 
GL_EXT_shared_texture_palette 
GLX_SGIS_blended_overlay 
GL_EXT_separate_specular_color 
GL_EXT_secondary_color 
GL_EXT_texture_env 
GL_EXT_texture_perturb_normal 
GL_EXT_multi_draw_arrays 
GL_EXT_fog_coord 
GL_REND_screen_coordinates 
GL_EXT_coordinate_frame 
GL_EXT_texture_env_combine 
GL_APPLE_specular_vector 
GL_APPLE_transform_hint 
GL_SUNX_constant_data 
GL_SUN_global_alpha 
GL_SUN_triangle_list 
GL_SUN_vertex 
WGL_EXT_display_color_table 
WGL_EXT_extensions_string 
WGL_EXT_make_current_read 
WGL_EXT_pixel_format 
WGL_EXT_pbuffer 
WGL_EXT_swap_control 
GL_EXT_blend_func_separate 
GL_INGR_color_clamp 
GL_INGR_interlace_read 
GL_EXT_stencil_wrap 
WGL_EXT_depth_float 
GL_EXT_422_pixels 
GL_NV_texgen_reflection 
GL_SGIX_texture_range 
GL_SUN_convolution_border_modes 
GLX_SUN_get_transparent_index 
GL_EXT_texture_env_add 
GL_EXT_texture_lod_bias 
GL_EXT_texture_filter_anisotropic 
GL_EXT_vertex_weighting 
GL_NV_light_max_exponent 
GL_NV_vertex_array_range 
GL_NV_register_combiners 
GL_NV_fog_distance 
GL_NV_texgen_emboss 
GL_NV_blend_square 
GL_NV_texture_env_combine4 
GL_MESA_resize_buffers 
GL_MESA_window_pos 
GL_EXT_texture_compression_s3tc 
GL_IBM_cull_vertex 
GL_IBM_multimode_draw_arrays 
GL_IBM_vertex_array_lists 
GL_3DFX_texture_compression_FXT1 
GL_3DFX_multisample 
GL_3DFX_tbuffer 
WGL_EXT_multisample 
GL_SGIX_vertex_preclip 
GL_SGIX_resample 
GL_SGIS_texture_color_mask 
GLX_MESA_copy_sub_buffer 
GLX_MESA_pixmap_colormap 
GLX_MESA_release_buffers 
GLX_MESA_set_3dfx_mode 
GL_EXT_texture_env_dot3 
GL_ATI_texture_mirror_once 
GL_NV_fence 
GL_IBM_static_data 
GL_IBM_texture_mirrored_repeat 
GL_NV_evaluators 
GL_NV_packed_depth_stencil 
GL_NV_register_combiners2 
GL_NV_texture_compression_vtc 
GL_NV_texture_rectangle 
GL_NV_texture_shader 
GL_NV_texture_shader2 
GL_NV_vertex_array_range2 
GL_NV_vertex_program 
GLX_SGIX_visual_select_group 
GL_SGIX_texture_coordinate_clamp 
GLX_OML_swap_method 
GLX_OML_sync_control 
GL_OML_interlace 
GL_OML_subsample 
GL_OML_resample 
WGL_OML_sync_control 
GL_NV_copy_depth_to_color 
GL_ATI_envmap_bumpmap 
GL_ATI_fragment_shader 
GL_ATI_pn_triangles 
GL_ATI_vertex_array_object 
GL_EXT_vertex_shader 
GL_ATI_vertex_streams 
WGL_I3D_digital_video_control 
WGL_I3D_gamma 
WGL_I3D_genlock 
WGL_I3D_image_buffer 
WGL_I3D_swap_frame_lock 
WGL_I3D_swap_frame_usage 
GL_ATI_element_array 
GL_SUN_mesh_array 
GL_SUN_slice_accum 
GL_NV_multisample_filter_hint 
GL_NV_depth_clamp 
GL_NV_occlusion_query 
GL_NV_point_sprite 
WGL_NV_render_depth_texture 
WGL_NV_render_texture_rectangle 
GL_NV_texture_shader3 
GL_NV_vertex_program1_1 
GL_EXT_shadow_funcs 
GL_EXT_stencil_two_side 
GL_ATI_text_fragment_shader 
GL_APPLE_client_storage 
GL_APPLE_element_array 
GL_APPLE_fence 
GL_APPLE_vertex_array_object 
GL_APPLE_vertex_array_range 
GL_APPLE_ycbcr_422 
GL_S3_s3tc 
GL_ATI_draw_buffers 
WGL_ATI_pixel_format_float 
GL_ATI_texture_env_combine3 
GL_ATI_texture_float 
GL_NV_float_buffer 
GL_NV_fragment_program 
GL_NV_half_float 
GL_NV_pixel_data_range 
GL_NV_primitive_restart 
GL_NV_texture_expand_normal 
GL_NV_vertex_program2 
GL_ATI_map_object_buffer 
GL_ATI_separate_stencil 
GL_ATI_vertex_attrib_array_object 
GL_OES_byte_coordinates 
GL_OES_fixed_point 
GL_OES_single_precision 
GL_OES_compressed_paletted_texture 
GL_OES_read_format 
GL_OES_query_matrix 
GL_EXT_depth_bounds_test 
GL_EXT_texture_mirror_clamp
GL_EXT_blend_equation_separate 
GL_MESA_pack_invert 
GL_MESA_ycbcr_texture
GL_EXT_pixel_buffer_object
GL_NV_fragment_program_option
GL_NV_fragment_program2
GL_NV_vertex_program2_option
GL_NV_vertex_program3
GLX_SGIX_hyperpipe
GLX_MESA_agp_offset
GL_EXT_texture_compression_dxt1
GL_EXT_framebuffer_object
GL_GREMEDY_string_marker
GL_EXT_packed_depth_stencil
GL_EXT_stencil_clear_tag
GL_EXT_texture_sRGB
GL_EXT_framebuffer_blit
GL_EXT_framebuffer_multisample
GL_MESAX_texture_stack
GL_EXT_timer_query
GL_EXT_gpu_program_parameters
GL_APPLE_flush_buffer_range
GL_EXT_bindable_uniform
GL_EXT_draw_buffers2
GL_EXT_draw_instanced
GL_EXT_framebuffer_sRGB
WGL_EXT_framebuffer_sRGB
GLX_EXT_framebuffer_sRGB
GL_EXT_geometry_shader4
GL_EXT_gpu_shader4
GL_EXT_packed_float
WGL_EXT_packed_float
GLX_EXT_packed_float
GL_EXT_texture_array
GL_EXT_texture_buffer_object
GL_EXT_texture_compression_latc
GL_EXT_texture_compression_rgtc
GL_EXT_texture_integer
GL_EXT_texture_shared_exponent
GL_NV_depth_buffer_float
GL_NV_fragment_program4
GL_NV_framebuffer_multisample_coverage
GL_NV_geometry_program4
GL_NV_gpu_program4
GL_NV_parameter_buffer_object
GL_NV_transform_feedback
GL_NV_vertex_program4
GL_GREMEDY_frame_terminator