[add GcRoots case to traversal functions
John Meacham <john@repetae.net>**20110704043925
 Ignore-this: 970550285354bb17fac624168bb5642b
] hunk ./src/Grin/Whiz.hs 87
+    g env (GcRoots vs body) = do
+        vs <- mapM (applySubst env) vs
+        body <- f body [] env
+        return $ GcRoots vs body
hunk ./src/Grin/Whiz.hs 160
+    g env (GcRoots vs body) = do
+        vs <- mapM (applySubst env) vs
+        body <- f body [] env
+        return $ GcRoots vs body