A type vector with multiple IC types needs metadata.

This CL adds a bitset to describe the type of IC in each IC slot.
This is necessary for clearing ICs of different types.

With FLAG_vector_ics off (the current state), it's not required because
CALL_IC is the only type of IC in the vector.

R=ishell@chromium.org

Review URL: https://codereview.chromium.org/679073002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24911 ce2b1a6d-e550-0410-aec6-3dcde31c8c00