The EXT spec has been updated to:
 - logically combine the es2_profile and es_profile exts
 - allow any legal version to be requested

dEQP tests request a specific ES version when using GLX, so this allows
dEQP upstream to run against GLX with the appropriate X server patch
(which had similar disabling logic).

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Matt Turner <mattst88@gmail.com> (v1)
Reviewed-by: Adam Jackson <ajax@redhat.com> (v3)

v1 -> v2:
 - distinguish between DRI_API_GLES{,2,3}
 - add GLX_EXT_create_context_es_profile client-side support
v2 -> v3:
 - fix error in computing mask