Fix possible threading problems, by using proper class finalizer, and

Fix possible threading problems, by using proper class finalizer, and

	* gp11/gp11-private.h:
	* gp11/gp11-call.c: Fix possible threading problems, by using
	proper class finalizer, and hiding all instance details.

	* gp11/gp11-object.c: Fix possible reference counting problem.

	* gp11/gp11-slot.c:
	* gp11/tests/unit-test-gp11-object.c: Fix test reference problems.

svn path=/trunk/; revision=1402