pycompat: avoid using an extra function

We have a single line function which just lowercase the letters and replaces
"_" with "". Its better to avoid that function call. Moreover we calling this
 function around 33 times.

mercurial/pycompat.py

@@ -41,11 +41,10 b' def _alias(alias, origin, items):'
 
     copies items from origin to alias
     """
-    def hgcase(item):
-        return item.replace('_', '').lower()
     for item in items:
         try:
-            setattr(alias, hgcase(item), getattr(origin, item))
+            lcase = item.replace('_', '').lower()
+            setattr(alias, lcase, getattr(origin, item))
         except AttributeError:
             pass