* cygwin.din (ualarm): New export.

* dcrt0.cc (_dll_crt0): Add experimental tls storage declaration.
(dll_crt0): Ditto.
* debug.cc (thread_stub): Ditto.
* thread.cc: Minor cleanup.
(__pthread_create): Add experimental tls storage declaration.
* miscfuncs.cc: Define tls index.
* winsup.h: Declare experimental tls storage.
* window.cc (alarm): Use old timer return from setitimer.
(ualarm): New function.

winsup/cygwin/dcrt0.cc

@@ -803,6 +803,7 @@ initial_env ()
 extern "C" void __stdcall
 _dll_crt0 ()
 {
+  DECLARE_TLS_STORAGE;
   initial_env ();
   char zeros[sizeof (fork_info->zero)] = {0};
 #ifdef DEBUGGING
@@ -853,6 +854,7 @@ _dll_crt0 ()
 void
 dll_crt0 (per_process *uptr)
 {
+  DECLARE_TLS_STORAGE;
   /* Set the local copy of the pointer into the user space. */
   if (uptr && uptr != user_data)
     {