CompletionItem: consistent self variable names
CompletionItem: consistent self variable names

"self" is rarely used as a self variable name in GtkSourceView, usually
a more precise name is used, related to the class.

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