Fix ipipe/ibrowse bug on OSX.

Note that ipipe still needs updating to come out of deathrow, but since I
made this fix for the 0.10.1 branch, I want to keep it updated in trunk at
least.

Closes https://bugs.launchpad.net/ipython/+bug/566675

IPython/deathrow/ibrowse.py

@@ -1757,7 +1757,7 b' class ibrowse(ipipe.Display):'
         self.scr = None
 
     def display(self):
-        if hasattr(curses, "resize_term"):
+        if hasattr(curses, "resize_term") and hasattr(signal, 'SIGWINCH'):
             oldhandler = signal.signal(signal.SIGWINCH, self.sigwinchhandler)
             try:
                 return curses.wrapper(self._dodisplay)