Disable templetized operators by default

To avoid nasty bugs due to silently overriding of
common operator we enable the templates on a type
by type base using partial template specialization.

No functional change, zero overhead at runtime.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/direction.h

@@ -45,6 +45,8 @@ enum SignedDirection {
   SIGNED_DIR_NONE = 8
 };
 
+ENABLE_OPERATORS_ON(SignedDirection);
+
 
 ////
 //// Variables