2003-05-17  Martin Baulig  <martin@ximian.com>

	* include/gc.h (GCThreadFunctions): New function vtable to allow a
	client to provide custom versions of stopping/starting the world.

	* linux_threads.c (GC_stop_world): Moved the functionality into
	linux_stop_world(); just call it via the `gc_thread_vtable' here.
	(GC_start_world, GC_push_all_stacks): Likewise.