Refactoring out old code, missing things for debug builds

[Tristan Van Berkom <tristanvb openismus com>]

Guys, 
   I'm just raising this because it's been the third time now
that I have to fix people's refactor commits locally just to get
through a build.

Today it was:
gdkvisual-x11.c: In function ‘_gdk_visual_init’:
gdkvisual-x11.c:283: error: ‘GdkVisual’ has no member named ‘visual’
gdkvisual-x11.c:283: error: ‘GdkVisual’ has no member named ‘visual’

Due to some code inside #ifdef G_ENABLE_DEBUG

Please; when doing mass commits to GTK+ that change API, please make
sure you have configured with --enable-debug.

Thanks,
    -Tristan