Implement yield-from in Python 2.x as a macro

  And who said you can't teach an old dog new tricks.

  ... but at the same time, drop Python 3.2 for not knowing this new
  trick.
Fix yield-from test indentation

Indentation was inconsistent with our usual indentation style.
Test to ensure exception handling in yield-from works right
Forgot to undo the second tianon. Whoops.