[add mfindWithDefault and mmapWithKey
John Meacham <john@repetae.net>**20080222055037] hunk ./Util/SetLike.hs 9
+    mfindWithDefault,
hunk ./Util/SetLike.hs 154
+    mmapWithKey :: (k -> v -> v) -> m -> m
hunk ./Util/SetLike.hs 172
+    mmapWithKey = IM.mapWithKey
hunk ./Util/SetLike.hs 184
+    mmapWithKey = M.mapWithKey
hunk ./Util/SetLike.hs 188
+mfindWithDefault d k m = case mlookup k m of
+    Nothing -> d
+    Just x -> x