autoconf: Make header install distinct for various APIs (v2)

This fixes a problem where GL headers would only get installed if
glx was enabled.  So if osmesa was enabled but not glx, then the
GL headers required by osmesa would be missing from the install.

v2: Dropped unneeded mesa_glinterop.h redundant osmesa.h install

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Chuck Atkins <chuck.atkins@kitware.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
3 files changed