The HGlobalValueNumberer class is renamed to HGlobalValueNumberingPhase,
following the naming scheme suggested by danno@chromium.org in
https://codereview.chromium.org/17458002

The GVN phase now uses the phase zone for all its allocations.

Depends upon https://codereview.chromium.org/18022002

R=danno@chromium.org
BUG=

Review URL: https://codereview.chromium.org/17657004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15353 ce2b1a6d-e550-0410-aec6-3dcde31c8c00