add isDedicatedSupportingCoreProfiles function

this function should be used to check if the afns driver is supporting core profiles

v2: remove if statemant by simply returning
test implementation of GLX_ARB_create_context

I don't think this should be it at all. But it can be used to create Core profiles where needed. This commit does not claim perfect implementation, just use it at own risk, if you really need this

v2: rebase on master (adding GLX_SGIX_pbuffer)
v3: rebase on master

fixup