[add FreeVars instances for function definitions and props
John Meacham <john@repetae.net>**20060815030736] hunk ./Grin/Grin.hs 596
+instance FreeVars FuncProps (Set.Set Var) where
+    freeVars FuncProps { funcFreeVars = fv } = fv
+
+instance FreeVars FuncProps (Set.Set Tag) where
+    freeVars FuncProps { funcTags = fv } = fv
+
+instance FreeVars FuncProps a => FreeVars FuncDef a where
+    freeVars fd = freeVars (funcDefProps fd)