[add union and unions
John Meacham <john@repetae.net>**20060408060613] hunk ./Util/SetLike.hs 5
+    union,
+    unions,
hunk ./Util/SetLike.hs 54
+union :: SetLike a => a -> a -> a
+union = mappend
+
+unions :: SetLike a => [a] -> a
+unions = mconcat
+