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.

Config/Cost.hs

@@ -52,7 +52,7 @@ insertCostAfter l pos
 	| otherwise =
 		firstsegment ++ [costBetween item nextitem ] ++ lastsegment
   where
-  	nextpos = pos + 1
+	nextpos = pos + 1
 	maxpos = length l - 1
 	
 	item = l !! pos