This is a first step towards incremental code flushing. The code
flushing support is now shared between full and incremental marking.
The code flusher itself is not yet activated in incremental mode and
will require some additional adaptations.

R=ulan@chromium.org
BUG=v8:1609

Review URL: https://codereview.chromium.org/11028016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12714 ce2b1a6d-e550-0410-aec6-3dcde31c8c00