[add pretty printing method for HsClassHead
John Meacham <john@repetae.net>**20080218143804] hunk ./FrontEnd/HsPretty.hs 237
+ppClassHead :: HsClassHead -> Doc
+ppClassHead (HsClassHead c n ts) = ans c where
+    ans [] = f n ts
+    ans c = ppHsContext c <+> text "=>" <+> f n ts
+    f n ts = ppHsType (foldl HsTyApp (HsTyCon n)  ts)
+
hunk ./FrontEnd/HsPretty.hs 245
+ppHsDecl (HsDeclDeriving _ e) = text "derive instance" <+> ppClassHead e