MIPS: Check that external references are registered in the serializer.

Port r22896 (4e54978a)

BUG=
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/444943002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22919 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix windows build.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/444953002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22920 ce2b1a6d-e550-0410-aec6-3dcde31c8c00