[gtk] Non-fast-forward update to branch win32-check-shader-support

[Chun-wei Fan <fanchunwei src gnome org>]

The branch 'win32-check-shader-support' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  4c04810... GDK-Win32: Reject GL context if shaders aren't supported
  f8d976d... GDK-Win32: Correct the check for GL_ARB_shader_objects
  28075f8... GDK-Win32: Remove check for shader support in GLES

Commits added to the branch:

  5d0f188... GDK-Win32: Reject WGL context if shaders aren't supported