gtk/gtkcsstypesprivate.h: Fix Build
gtk/gtkcsstypesprivate.h: Fix Build

The recent change to the enum declaration for GtkCssChange actually
relied on compiler-dependent behavior, which also breaks the build on
some non-GCC compilers, such as Visual Studio.  As noted in the
G_STATIC_ASSERT line just beneath this declaration, we need to change
this enum declaration to #define's, in order to fix the build in such
situations.

https://bugzilla.gnome.org/show_bug.cgi?id=752814

chergert/gtk,chergert/gtk,grubersjoe/adwaita,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,jadahl/gtk,jigpu/gtk,chergert/gtk,alexlarsson/gtk,chergert/gtk,jadahl/gtk,davidgumberg/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,jigpu/gtk,jigpu/gtk,chergert/gtk,alexlarsson/gtk,jadahl/gtk,chergert/gtk,grubersjoe/adwaita,chergert/gtk,davidgumberg/gtk,grubersjoe/adwaita,alexlarsson/gtk,alexlarsson/gtk,jigpu/gtk,jadahl/gtk,davidgumberg/gtk,jigpu/gtk,grubersjoe/adwaita,alexlarsson/gtk,grubersjoe/adwaita,davidgumberg/gtk,jadahl/gtk,grubersjoe/adwaita,jigpu/gtk,davidgumberg/gtk,jigpu/gtk,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,alexlarsson/gtk,jigpu/gtk