Serve cabal files as text/plain (fixes haskell#176)

Author: bergmark

Distribution/Server/Framework/HappstackUtils.hs

@@ -52,7 +52,11 @@ uriEscape = URI.escapeURIString URI.isAllowedInURI
 mime :: FilePath -> String
 mime x  = Map.findWithDefault "text/plain; charset=utf-8" (drop 1 (takeExtension x)) mimeTypes'
   where
-    mimeTypes' = mimeTypes `Map.union` Map.fromList [("xhtml", "application/xhtml+xml")]
+    mimeTypes' = customMimeTypes `Map.union` mimeTypes
+    customMimeTypes = Map.fromList
+      [ ("xhtml", "application/xhtml+xml")
+      , ("cabal", "text/plain")
+      ]