glapi: Don't emit remap data for individual extensions

glapi: Don't emit remap data for individual extensions

All of the extensions actually supported by Mesa have been remapped by
remap.c for a long time.  Emitting all of these data structures is
just clutter.

Drivers that need additional functions remapped, should add
'offset="assign"' to the function definition in the .xml file.

The changes to remap_helper.h are in a follow-on ~8700 line patch that
would surely be rejected by the mailing list.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Chia-I Wu <olv@lunarg.com>