tgsi: replace tgsi_file_names tgsi_file_names[] with tgsi_file_name() function

This change came from the discovery that the STATIC_ASSERT to check that
the number of register file strings didn't actually work.

Similar changes could be made for the other string arrays in tgsi_string.c

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
gallium: Remove draw_arrays() and draw_arrays_instanced() functions

Moved draw_arrays() to st_draw_feedback.c and removed draw_arrays_instanced().
draw_arrays() was used by nobody else.  Now there's just one "draw" entrypoint
into the draw module.

Signed-off-by: Brian Paul <brianp@vmware.com>
docs: update some environment variable info

Drop the GALLIUM_NOSSE/PPC env vars, added ST_DEBUG and some of the
VMware SVGA driver env vars.