This allows us to remove a lot of #ifdef's. Either we want to use
a config.h or we don't. Since we'll want it for e.g. optional gsound
support later on let's have it.
- use G_DECLARE_ and G_DEFINE_ macros
- move all data into ClassNamePrivate
- use _get_instance_private()
This should not introduce any functional changes or breakage.
Skipped two classes (EekKeyboard and EekboardContextService) for now in
order not to break the build.
These two classes are used in some very funky WIP code that tries to
circumvent encapsulation.
(Funky code is in eekboard/key-emitter.c and eekboard/eekboard-context-service.c)
