Flesh out vector ic state query and set mechanisms.

The IC system now fully integrates the vector concept and can
handle loads and keyed loads vector-based.

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/754303003

Cr-Commit-Position: refs/heads/master@{#25552}
Set clang directory in gyp.

BUG=

Review URL: https://codereview.chromium.org/764803002

Cr-Commit-Position: refs/heads/master@{#25553}