Use the wgl* entrypoints instead of the GDI entrypoints when TRACE_LIBGL is set.
Use the wgl* entrypoints instead of the GDI entrypoints when TRACE_LIBGL is set.

This enables testing multiple OpenGL implementations on Windows without
installing.  Useful to use retracediff.py script on Windows.

surround-io/apitrace,PeterLValve/apitrace,joshua5201/apitrace,EoD/apitrace,swq0553/apitrace,tuanthng/apitrace,joshua5201/apitrace,tuanthng/apitrace,swq0553/apitrace,tuanthng/apitrace,joshua5201/apitrace,apitrace/apitrace,apitrace/apitrace,schulmar/apitrace,apitrace/apitrace,schulmar/apitrace,surround-io/apitrace,trtt/apitrace,tuanthng/apitrace,PeterLValve/apitrace,surround-io/apitrace,tuanthng/apitrace,EoD/apitrace,EoD/apitrace,EoD/apitrace,PeterLValve/apitrace,schulmar/apitrace,swq0553/apitrace,trtt/apitrace,surround-io/apitrace,schulmar/apitrace,swq0553/apitrace,EoD/apitrace,PeterLValve/apitrace,joshua5201/apitrace,swq0553/apitrace,surround-io/apitrace,schulmar/apitrace,apitrace/apitrace,joshua5201/apitrace,trtt/apitrace,trtt/apitrace,trtt/apitrace