Encapsulate type information in a convenient wrapper instead of storing it in a naked bitfield. This especially facilitates transitioning to a new state and converting from/to the extraICState representation. Additionally cleaning up ToBooleanICStub::Types for consistency.

BUG=
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/14862009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14704 ce2b1a6d-e550-0410-aec6-3dcde31c8c00