[Mesa-dev] classic driver cleanup: ChooseTexFormat

[Eric Anholt]

One of the uglier bits of the classic drivers, in my opinion, is the
ChooseTexFormat hook.  Most drivers are trying to get to a similar set
of formats, and using similar fallbacks for unavailable formats.
Worse, they need to cleverly choose formats based on the incoming
type/format to avoid having to munge the data on the way in if
possible, and everyone needs to work those out.  So, rather than
having each driver have these smarts, move it to the core.

There are still some rough edges.  There are not enough fallbacks yet
to cover everything (see i810 for example), so drivers with a more
restricted set of supported formats may need to add more lines to
_mesa_choose_tex_format.  Also, the endianness-dependent choice of
formats in texmem.c and radeon's texturing isn't merged -- I knew I'd
mess it up somehow if I did it on my own, so I'm leaving radeon for
someone with big-endian to finish off.

Any complaints, or should I go ahead and merge this?