Express LoadIC extra ic state with LoadIC::State

Soon we will create code stubs that need to match LoadIC state. It's easier to
express if the state is encapsulated in a single class rather than multiple bit
fields.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/415543002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22559 ce2b1a6d-e550-0410-aec6-3dcde31c8c00