fix some mixed space+tab indentation

This fixes all instances of " \t" in the code base. Most common case
seems to be after a "where" line; probably vim copied the two space layout
of that line.

Done as a background task while listening to episode 2 of the Type Theory
podcast.

Utility/Directory.hs

@@ -56,7 +56,7 @@ dirContentsRecursive = dirContentsRecursiveSkipping (const False) True
 dirContentsRecursiveSkipping :: (FilePath -> Bool) -> Bool -> FilePath -> IO [FilePath]
 dirContentsRecursiveSkipping skipdir followsubdirsymlinks topdir = go [topdir]
   where
-  	go [] = return []
+	go [] = return []
 	go (dir:dirs)
 		| skipdir (takeFileName dir) = go dirs
 		| otherwise = unsafeInterleaveIO $ do
@@ -87,7 +87,7 @@ dirContentsRecursiveSkipping skipdir followsubdirsymlinks topdir = go [topdir]
 dirTreeRecursiveSkipping :: (FilePath -> Bool) -> FilePath -> IO [FilePath]
 dirTreeRecursiveSkipping skipdir topdir = go [] [topdir]
   where
-  	go c [] = return c
+	go c [] = return c
 	go c (dir:dirs)
 		| skipdir (takeFileName dir) = go c dirs
 		| otherwise = unsafeInterleaveIO $ do