Merged r15047, r15048, r15049 into trunk branch.

MIPS: add a default value for return value

MIPS: Fix LoadIC calling convention.

MIPS: Generator object "next" method takes optional send value.

BUG=v8:2355, v8:2715

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/16703007

git-svn-id: https://v8.googlecode.com/svn/trunk@15051 ce2b1a6d-e550-0410-aec6-3dcde31c8c00