* include/gc_pthread_redirects.h: Generalize test to use GC_PTHREADS.
	* linux_threads.c (WRAP_FUNC(pthread_join)): Conditionalized on
	GC_FREEBSD_THREADS, handle strange interaction between system
	pthread implementation and boehm-gc signal-handler architecture.
	* tests/test.c (main): Conditionalized on GC_FREEBSD_THREADS,
	set stack.
	* include/private/gcconfig.h (configuration keyed off FREEBSD):
	Define SIG_SUSPEND, SIG_THR_RESTART.  Do not define
	MPROTECT_VDB when GC_FREEBSD_THREADS is defined.

From-SVN: r46307