crecord: restore SIGWINCH handler before return

Previously, the SIGWINCH handler does not get cleared and if the commit
message editor also needs SIGWINCH handling (like vim), the two SIGWINCH
handlers (the editor's, ours) will have a race. And we may erase the
editor's screen content.

This patch restores SIGWINCH handler to address the above issue.

mercurial/crecord.py

@@ -1263,7 +1263,6 b' class curseschunkselector(object):'
             self.statuswin.resize(self.numstatuslines, self.xscreensize)
             self.numpadlines = self.getnumlinesdisplayed(ignorefolding=True) + 1
             self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
-            # todo: try to resize commit message window if possible
         except curses.error:
             pass
 
@@ -1589,7 +1588,8 b' are you sure you want to review/edit and'
         method to be wrapped by curses.wrapper() for selecting chunks.
         """
 
-        signal.signal(signal.SIGWINCH, self.sigwinchhandler)
+        origsigwinchhandler = signal.signal(signal.SIGWINCH,
+                                            self.sigwinchhandler)
         self.stdscr = stdscr
         # error during initialization, cannot be printed in the curses
         # interface, it should be printed by the calling code
@@ -1640,3 +1640,4 b' are you sure you want to review/edit and'
                 keypressed = "foobar"
             if self.handlekeypressed(keypressed):
                 break
+        signal.signal(signal.SIGWINCH, origsigwinchhandler)