[add substMap'' back in
John Meacham <john@repetae.net>**20080220050203] hunk ./E/Subst.hs 10
+    substMap'',
hunk ./E/Subst.hs 79
+-- | doesn't seed with free variables.
+substMap'' :: IdMap (Maybe E) -> E -> E
+substMap'' im = doSubst' False False (mapMaybeIdMap id im) (`mmember` im)
+