Always free locally defined macros when they go out of scope

Always free locally defined macros when they go out of scope
- Prior to this, local defines in constructs like %{!?foo: %define foo bar}
  would remain defined until a parametrized macro gets called, causing
  obscure and confusing errors in specs such as RhBug:551971 and countless
  others. Use of %global is now always required for such constructs.