Note to other developers: you might have to do `make clean;./autogen.sh`
after this commit.
* Use a GtkCheese namespace to be constistent with other vapi's (such as
GtkClutter).
* Put each library in a separate vapi-file (this will come in handy when
porting to Meson).
* Clean up config.vapi:
* get rid of unused CCode prefix-attribute (removes warning)
* be consistent with braces