Call GetRealFunctions on MakeCurrent to populate extensions.

* Even if the app only queries some subset of extensions, we may need
  more (e.g. need the DSA extensions). GetRealFunctions does a
  PopulateHooks which will fill out the extensions that we need.

renderdoc/hooks/gl_win32_hooks.cpp

@@ -339,6 +339,8 @@ class OpenGLHook : LibraryHook
 
 			glhooks.GetDriver()->ActivateContext(WindowFromDC(dc), rc);
 
+			glhooks.GetRealFunctions();
+
 			return ret;
 		}