Prevent flushing of code that was set with %SetCode.

Prevent flushing of code that was set with %SetCode.

This makes sure that shared function infos that break the one-to-one
mapping to code are marked as un-flushable. Otherwise enqueuing through
the GC meta-data field in the code object doesn't work.

R=rossberg@chromium.org
TEST=cctest/test-api/Threading4

Committed: http://code.google.com/p/v8/source/detail?r=14635

[rossberg, 2013-05-13 10:40:11]

lgtm

[Michael Starzinger, 2013-05-13 10:59:07]

Committed patchset #1 manually as r14635 (presubmit successful).