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/ExternalSHA.hs

@@ -57,7 +57,7 @@ externalSHA command shasize file = do
 			Left $ "Unexpected character in output of " ++ command ++ "\"" ++ sha ++ "\""
 		| otherwise = Right sha'
 	  where
-	  	sha' = map toLower sha
+		sha' = map toLower sha
 
 expectedSHALength :: Int -> Int
 expectedSHALength 1 = 40