fancyopts: restore use of callable() since it was readded in Python 3.2

mercurial/fancyopts.py

@@ -77,7 +77,7 b' def fancyopts(args, options, state, gnu='
         # copy defaults to state
         if isinstance(default, list):
             state[name] = default[:]
-        elif getattr(default, '__call__', False):
+        elif callable(default):
             state[name] = None
         else:
             state[name] = default