MIPS: Split AccessorInfo into DeclaredAccessorInfo and ExecutableAccessorInfo

Port r13649 (0a9e0bf0)

BUG=

Review URL: https://codereview.chromium.org/12253005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13685 ce2b1a6d-e550-0410-aec6-3dcde31c8c00