[parrot/parrot] 5b125a: fix bug in Parrot_ext_try reported by kshannon++:

[noreply at github.com]

  Branch: refs/heads/master
  Home:   https://github.com/parrot/parrot

  Commit: 5b125a15682c2cef3bfd0a22da4bd8e4bbeb2c22
      https://github.com/parrot/parrot/commit/5b125a15682c2cef3bfd0a22da4bd8e4bbeb2c22
  Author: NotFound <julian.notfound at gmail.com>
  Date:   2012-01-03 (Tue, 03 Jan 2012)

  Changed paths:
    M src/extend.c

  Log Message:
  -----------
  fix bug in Parrot_ext_try reported by kshannon++:
the context pop was not poping at all.
The fix uses a static function instead of a macro for simplicity,
setjmp has much bigger impact in speed than any additional call