Call gl.ContextWatcher.OnMakeCurrent after making context current.
Call gl.ContextWatcher.OnMakeCurrent after making context current.

This is needed for Windows OpenGL backend, in place of previous direct
gl.Init call. We need to call it ourselves since this version of GLFW
does not take on this responsibility.

Drahoslav7/gxui,UIKit0/gxui,CodyGuo/gxui,leelib/gxui,xinhuang327/gxui,pombredanne/gxui,Anaminus/gxui,treejames/gxui,insionng/gxui,henrikhodne/gxui,jmptrader/gxui,henrylee2cn/gxui,rnubel/gxui,abadojack/gxui,google/gxui,MeGaPk/gxui,mzgnr/gxui,cainiaocome/gxui,ylong/gxui