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/Batch.hs

@@ -32,7 +32,7 @@ batch :: IO a -> IO a
 #if defined(linux_HOST_OS) || defined(__ANDROID__)
 batch a = wait =<< batchthread
   where
-  	batchthread = asyncBound $ do
+	batchthread = asyncBound $ do
 		setProcessPriority 0 maxNice
 		a
 #else