[avoid a liftM in a hot path
Helmut Grohne <grohne@cs.uni-bonn.de>**20150416070712
 Ignore-this: b6c3ebdc3fc1f15a12a1b6411aed26c8
 
 This saves 3% on the first 2000 loops of mult and has little effect on anything
 else.
] hunk ./src/Syntax/UnifyExp.hs 61
-bindVarAU img = getMap >>= maybe (mkVar img) return . liftM snd . find matchimg
+bindVarAU img = getMap >>= maybe (mkVar img) (return . snd) . find matchimg