get the most commonly used commands building again

A quick benchmark of whereis shows not much speed improvement, maybe a
few percent. Profiling it found a hotspot, adds to todo.

Command/Sync.hs

@@ -7,6 +7,7 @@
  -}
 
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE OverloadedStrings #-}
 
 module Command.Sync (
 	cmd,