Compilation type and state allocate an unnecessary Smi on v8::Script.

This patch combines them into a single field, and adjusts the accessors
and setters to take the enum type directly, rather than converting to and
from a Smi value.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/20758002

Patch from Mike West <mkwst@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15940 ce2b1a6d-e550-0410-aec6-3dcde31c8c00