buffer: make code a bit clearer for the context class mask
buffer: make code a bit clearer for the context class mask

- Move the variable inside the function, so there is one less global
variable.
- Use G_N_ELEMENTS().
- Better function and variable names.

cburschka/gtksourceview,cburschka/gtksourceview,uajain/gtksourceview,uajain/gtksourceview,uajain/gtksourceview,GNOME/gtksourceview,GNOME/gtksourceview,GNOME/gtksourceview,GNOME/gtksourceview,GNOME/gtksourceview,GNOME/gtksourceview,cburschka/gtksourceview,uajain/gtksourceview,uajain/gtksourceview,uajain/gtksourceview,GNOME/gtksourceview,uajain/gtksourceview,uajain/gtksourceview,GNOME/gtksourceview,cburschka/gtksourceview,cburschka/gtksourceview,cburschka/gtksourceview,GNOME/gtksourceview,cburschka/gtksourceview,GNOME/gtksourceview,uajain/gtksourceview,cburschka/gtksourceview,uajain/gtksourceview,GNOME/gtksourceview,GNOME/gtksourceview,cburschka/gtksourceview,cburschka/gtksourceview,GNOME/gtksourceview,GNOME/gtksourceview,GNOME/gtksourceview