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.

Annex/View/ViewedFile.hs

@@ -58,7 +58,7 @@ viewedFileReuse = takeFileName
 dirFromViewedFile :: ViewedFile -> FilePath
 dirFromViewedFile = joinPath . drop 1 . sep [] ""
   where
-  	sep l _ [] = reverse l
+	sep l _ [] = reverse l
 	sep l curr (c:cs)
 		| c == '%' = sep (reverse curr:l) "" cs
 		| c == '\\' = case cs of