Collect garbage before running mjsunit/fast-prototype

Collect garbage before running mjsunit/fast-prototype

When not using a snapshot, after turning on i18n, there's just enough
garbage after creating a context to trigger gc at the wrong moment.
Since the test uses natives syntax to access information that would
otherwise be hidden from javascript, this makes the test fail

BUG=none
R=mstarzinger@chromium.org
TEST=mjsunit/fast-prototype passes on ia32.release with no snapshot

Committed: https://code.google.com/p/v8/source/detail?r=16830

[Michael Starzinger, 2013-09-19 13:11:25]

LGTM.

[jochen (gone - plz use gerrit), 2013-09-19 13:12:04]

Committed patchset #1 manually as r16830.