crecord: avoid setting non-existing signal SIGWINCH on windows

Windows do not have a SIGWINCH so we avoid setting the handler if the signal is
unknown.

mercurial/crecord.py

@@ -1614,12 +1614,15 b' are you sure you want to review/edit and'
         method to be wrapped by curses.wrapper() for selecting chunks.
         """
 
-        origsigwinchhandler = signal.signal(signal.SIGWINCH,
-                                            self.sigwinchhandler)
+        origsigwinch = sentinel = object()
+        if util.safehasattr(signal, 'SIGWINCH'):
+            origsigwinch = signal.signal(signal.SIGWINCH,
+                                         self.sigwinchhandler)
         try:
             return self._main(stdscr)
         finally:
-            signal.signal(signal.SIGWINCH, origsigwinchhandler)
+            if origsigwinch is not sentinel:
+                signal.signal(signal.SIGWINCH, origsigwinch)
 
     def _main(self, stdscr):
         self.stdscr = stdscr