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/FileSystemEncoding.hs

@@ -111,7 +111,7 @@ truncateFilePath :: Int -> FilePath -> FilePath
 #ifndef mingw32_HOST_OS
 truncateFilePath n = go . reverse
   where
-  	go f =
+	go f =
 		let bytes = decodeW8 f
 		in if length bytes <= n
 			then reverse f