* 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/debug.cc

@@ -82,6 +82,7 @@ thread_start NO_COPY start_buf[NTHREADS] = {{0, NULL,NULL}};
 static DWORD WINAPI
 thread_stub (VOID *arg)
 {
+  DECLARE_TLS_STORAGE;
   LPTHREAD_START_ROUTINE threadfunc = ((thread_start *) arg)->func;
   VOID *threadarg = ((thread_start *) arg)->arg;