This is for the conversion /to/ paletted textures. The conversion is
necessary for csqc support. In the process, the conversion has been sped up
by implementing a color cache for the conversion process. I haven't
measured the difference yet, but Mr Fixit does seem to load much faster for
the sw renderer than it did before the change (many months old memory).
It now takes a context pointer (opaque data) that holds the buffers it
uses for the temporary strings. If the context pointer is null, a static
context is used (making those uses of va NOT thread-safe). Most calls to
va use the static context, but all such calls have been formatted
consistently so they are easy to find when it comes time to do a full
audit.
