Removed obsolete intermediate threading layer.

	* thr.c: Use __gthread_objc_xxx functions directly instead of
	__objc_thread_xxx ones.
	* objc/thr.h: Removed prototypes of no longer existing
	__objc_thread_xxx functions.
	* Makefile.in: Removed thr-objc.lo.
	* thr-dce.c: File removed.
	* thr-decosf1.c: File removed.
	* thr-irix.c: File removed.
	* thr-mach.c: File removed.
	* thr-objc.c: File removed.
	* thr-os2.c: File removed.
	* thr-posix.c: File removed.
	* thr-pthreads.c: File removed.
	* thr-rtems.c: File removed.
	* thr-single.c: File removed.
	* thr-solaris.c: File removed.
	* thr-vxworks.c: File removed.
	* thr-win32.c: File removed.
	* README.threads: File removed.
	* THREADS.MACH: File removed.
	* THREADS: Updated.

From-SVN: r163996