automake: Convert dricore building to automake.

This is performed in a subdirectory to avoid needing to convert all of
src/mesa/Makefile in one go.

I can now cherry-pick a commit containing glapi XML changes, do "(cd
src/mapi/glapi/gen && make) && make", and get a working driver.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
4 files changed