sortdict: have update() accept either dict or iterable of key/value pairs

Future patches will make the templater store a sorted dict in the _hybrid object.
sortdict should be constructed from a sorted list.

mercurial/util.py

@@ -359,8 +359,10 b' class sortdict(dict):'
     def __iter__(self):
         return self._list.__iter__()
     def update(self, src):
-        for k in src:
-            self[k] = src[k]
+        if isinstance(src, dict):
+            src = src.iteritems()
+        for k, v in src:
+            self[k] = v
     def clear(self):
         dict.clear(self)
         self._list = []