eglGetDisplay forces the implementation to guess which kind of display
it's been handed. glvnd does something different from Mesa, and in
general it's impossible for the library to get this right. Add a new
inline that gets the logic right, and works around a quirk in epoxy.
Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
