In libobjc/: Implemented objc_sync_enter() and objc_sync_exit(), which are required by @synchronized() to work.

In libobjc/:
       Implemented objc_sync_enter() and objc_sync_exit(), which are
       required by @synchronized() to work.
       * objc-sync.c: New file.
       * objc/objc-sync.h: New file.
       * objc-private/objc-sync.h: New file.
       * init.c (__objc_exec_class): Call __objc_sync_init() during the
       Objective-C runtime startup.
       * Makefile.in: Added objc-sync.c and objc-sync.h.
       * configure.ac: Added GCC_CHECK_TLS.
       * acinclude.m4: Include ../config/enable.m4 and ../config/tls.m4.
       * configure: Regenerated.
       * config.h.in: Regenerated.

From-SVN: r164276
diff --git a/libobjc/configure.ac b/libobjc/configure.ac
index 8820edc..ed532fa 100644
--- a/libobjc/configure.ac
+++ b/libobjc/configure.ac
@@ -215,6 +215,8 @@
         [Define if the compiler has a thread header that is non single.])
 fi 
 
+# Check if we have thread-local storage
+GCC_CHECK_TLS
 
 AC_MSG_CHECKING([for exception model to use])
 AC_LANG_PUSH(C)