Refactor Hydrogen environment liveness analysis into an HPhase.

Refactor Hydrogen environment liveness analysis into an HPhase.

Rename EnvironmentSlotLivenessAnalyzer to HEnvironmentLivenessAnalysisPhase,
following naming scheme suggested by danno@chromium.org in
https://codereview.chromium.org/17458002

The environment slot liveness analysis now uses the phase zone for
all its allocations.

Depends on https://codereview.chromium.org/18034003

R=danno@chromium.org
BUG=

Review URL: https://codereview.chromium.org/17587008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15356 ce2b1a6d-e550-0410-aec6-3dcde31c8c00