demandimport: backout fe31f834a9ff

Using a keyword argument here breaks zipimporter for at least some
versions of Python2.6 on Windows.

mercurial/demandimport.py

@@ -45,7 +45,7 b' class _demandmod(object):'
         if not self._module:
             head, globals, locals, after, level = self._data
             if level is not None:
-                mod = _origimport(head, globals, locals, level=level)
+                mod = _origimport(head, globals, locals, level)
             else:
                 mod = _origimport(head, globals, locals)
             # load submodules