Relative running order between traits blocks

[Agent Zhang]

Hello, everyone~

S04 doesn't explain the running order between the traits blocks FIRST,
ENTER, NEXT, LEAVE, and LAST. So I couldn't be sure whether or not my
tests in the Pugs test suit are correct. Please check out the
following test file, which also servers as the first sketch of my
proposal:

http://svn.openfoundry.org/pugs/t/closure_traits/in_loop.t

Luke pointed out on #perl6 that LAST should be fired off after LEAVE
if FIRST runs before ENTER. I think it's good to symmetry.

Comments are very welcome. Hopefully we can end up with some sane
conclusion, which can finally go into S04. :=)

Regards,
Agent