Use an enum of Flags internally in CompilationInfo.

This is a first step in cleaning up CompilationInfo; a subsequent logical step
would be to inline most is_* and Set* and Mark* calls so that most callers
can use call info.SetFlag(CompilationInfo::kMyFlag), or at the very least,
rename them all to be consistent with their enum flag names.

R=yangguo@chromium.org, bmeuer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/504163002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23408 ce2b1a6d-e550-0410-aec6-3dcde31c8c00