lib_mysqludf_xql_info()
	Output the library version.


xql_textdecl(string version, string encoding [, string standalone])
    Write a text declarion; <?xml version="1.0" encoding="iso-8859-1" standalone="yes"?>

xql_pi(string content AS target)
    Write processing instruction; <?xsl-stylesheet type="text/xml" href="yourstyle.xsl"?>
    
xql_dtd(string name [, string pubid, string sysid [, string subset]]])
    Write a DTD tag


xql_element(string name, [string content | string XML AS `xql:raw` | string CDATA AS `xql:cdata` [, string att_val AS `att_name`, ...]])
    Write element node with attributes.

xql_forest([string name_root AS `xql:root`,] string content AS name | string XML AS `xql:raw` | string CDATA AS `xql:cdata:%`, ...)
    Write an element for each name/content pair.
    Arguments named `xql:raw` and output of xql functions are inserted as raw XML.
    Arguments starting with `xql:cdata:` are inserted as CDATA sections.

xql_concat([string name_root AS `xql:root`,] string xml, ...)
    Concatenate xml.
    
xql_agg([string name_root AS `xql:root`,] [string name_child AS `xql:child`,] string content AS name | string XML AS `xql:raw` | string CDATA AS `xql:cdata:%`, ...)
   Group concatenate XML for each row.
   Normal arguments are inserted as XML nodes.
   Arguments named `xql:raw` and output of xql functions are inserted as raw XML.
   Arguments starting with `xql:cdata:` as name are inserted as CDATA sections.

xql_comment(string content)
    Write comment node
    
xql_cdata(string content)
    Write CDATA section node

xql_encode(string content)
    Encode special chars