[add 'sfilter' to ModifySet
John Meacham <john@repetae.net>**20080301035530] hunk ./Util/SetLike.hs 61
+    sfilter :: (t -> Bool) -> s -> s
hunk ./Util/SetLike.hs 86
-    toList s = IS.toList s
+    toList s   = IS.toList s
hunk ./Util/SetLike.hs 89
+    sfilter    = IS.filter
hunk ./Util/SetLike.hs 108
-    toList s = S.toList s
+    toList s   = S.toList s
hunk ./Util/SetLike.hs 111
+    sfilter    = S.filter
hunk ./Util/SetLike.hs 120
-    sempty      = IM.empty
+    sempty     = IM.empty
hunk ./Util/SetLike.hs 135
-    sempty      = M.empty
+    sempty     = M.empty
hunk ./Util/SetLike.hs 213
+    sfilter f (EnumSet s) = EnumSet $ IS.filter (f . toEnum)  s