Make concrete classes for individual call descriptors. The ic-convention classes that hold register specifications are merged into these new call descriptor classes, which should represent a final home for that information.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/527093002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23639 ce2b1a6d-e550-0410-aec6-3dcde31c8c00