gltrace: Add missing OS X prototypes.
gltrace: Add missing OS X prototypes.

For completeness.  Specially because theres no *GetProcAddress on OS X,
so there's no warning when an app uses them.

Even with this change, there's still a few obscure entrypoint missing.

trtt/apitrace,trtt/apitrace,schulmar/apitrace,schulmar/apitrace,apitrace/apitrace,trtt/apitrace,trtt/apitrace,apitrace/apitrace,schulmar/apitrace,schulmar/apitrace,apitrace/apitrace,apitrace/apitrace,trtt/apitrace,schulmar/apitrace