Cygwin: FIFO: allow take_ownership to be interrupted

Use cygwait in take_ownership to allow interruption while waiting to
become owner.  Return the cygwait return value or a suitable value to
indicate an error.

raw_read now checks the return value and acts accordingly.

winsup/cygwin/fhandler.h

@@ -1489,7 +1489,7 @@ public:
   void owner_lock () { shmem->owner_lock (); }
   void owner_unlock () { shmem->owner_unlock (); }
 
-  void take_ownership ();
+  DWORD take_ownership ();
   void reading_lock () { shmem->reading_lock (); }
   void reading_unlock () { shmem->reading_unlock (); }