fixes for hanging waiting_thread-t.c on windows

mysys/my_wincond.c:
  race condition: block gate could be left open forever, if cond_broadcast
  was done right after the last thread left WaitForMultipleObjects() on timeout
mysys/thr_rwlock.c:
  make rwlocks behave similar to their distant linux/solaris relatives

mysys/my_wincond.c

@@ -126,7 +126,7 @@ int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
   EnterCriticalSection(&cond->lock_waiting);
   cond->waiting--;
   
-  if (cond->waiting == 0 && result == (WAIT_OBJECT_0+BROADCAST))
+  if (cond->waiting == 0)
   {
     /*
       We're the last waiter to be notified or to stop waiting, so

mysys/thr_rwlock.c

@@ -89,7 +89,7 @@ int my_rw_rdlock(rw_lock_t *rwp)
   pthread_mutex_lock(&rwp->lock);
 
   /* active or queued writers */
-  while (( rwp->state < 0 ) || rwp->waiters)
+  while (( rwp->state < 0 ))
     pthread_cond_wait( &rwp->readers, &rwp->lock);
 
   rwp->state++;
@@ -101,7 +101,7 @@ int my_rw_tryrdlock(rw_lock_t *rwp)
 {
   int res;
   pthread_mutex_lock(&rwp->lock);
-  if ((rwp->state < 0 ) || rwp->waiters)
+  if ((rwp->state < 0 ))
     res= EBUSY;					/* Can't get lock */
   else
   {