* fix altivec IDCT (memset block to 0), optimize mmx idct memset too.

* things we dont implement yet
	* more verbose error reporting
	* decoding of 4:2:2 streams
	* export MC information (for XvMC or for error resilience)
	* export quantizer information (for postprocessing filters)
	* export header/picture/slice user data
	* dont crash on bad streams, make sure we can resync after a while
		* possible chunk buffer overflow while reading bits
		* dont just fprintf and exit
	* synchronization stuff
	* IDCT precision with sparse matrixes
	* sparc IDCT/MC optimizations; get rid of mlib code
	* support for still pictures (decode before receiving next startcode !)

* structural optimizations
	* integrate idct_add and idct_copy into the main idct routine
	* do yuv per sub-slice (probably big speed boost)
	* try different memory arrangements for pictures (yuyv, stride, ...)
	* once we have sync, call draw_frame before decoding I or P not after

* local optimizations
	* use restrict (__restrict__) pointers: int * restrict p;
	* reschedule altivec IDCT and MC routines for 7450 chips
	* try feig IDCT instead of MSSG c IDCT ?
	* review the use of static inline functions
	* improve MMX motion comp inner routines
	* optimize IDCT for very sparse input matrixes ?
	* optimize startcode search loop ?
	* bit parsing / DCT parsing optimizations

* clean up
	* clean up header file usage
	* clean up yuv2rgb for interlaced pictures (handling of uv)
	* clean up picture_t structure (some variables should be local ?)
	* clean up slice_init