Add proc symbol loading and helper functions for calling them, dealing with errors etc. So far no extension symbols are loaded, only the infrastructure is there. https://bugzilla.gnome.org/show_bug.cgi?id=773629
Add a MetaEgl meant to deal with EGL. It is intended to be use by EGL based renderers and handle extension symbols loading, handle errors etc. https://bugzilla.gnome.org/show_bug.cgi?id=773629