Removed pointer space to pointer space compaction check when migrating objects.

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/20279002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15871 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Don't duplicate ceiling() for every POSIX platform.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/20274002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15872 ce2b1a6d-e550-0410-aec6-3dcde31c8c00