Todo List

Code issues:
 - (?) Create a TokenFactory to prevent really long lines
 - Massive profiling
 - Fix IPv6 issues
 - Make URI validation routines tighter (especially mailto)
 - Distinguish between different types of URIs, for instance, a mailto URI
   in IMG SRC is nonsensical
 - Factor out Host validation to its own AttrDef

Enhancements:
 - Do fixes for Firefox's inability to handle COL alignment props (Bug 915)
 - Have lexers strip out HTML and BODY tags rather than choke