#29 Port Texture paint plug-in

[Maurits Rijk]

User has requested port of the following plug-in:

Texture Paint (an old plugin)
http://registry.gimp.org/plugin?id=405

[Maurits Rijk]

Logged In: YES
user_id=21209

Lowering priority because this isn't trivial and depends on
(unreleased) stuff like GtkGL#