MIPS: Introduce code stub constructors for stub keys.

Port r23716 (9118048)

BUG=
R=dusan.milosavljevic@imgtec.com

Review URL: https://codereview.chromium.org/535373003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23721 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix EvacuateJSFunction to obtain the target address from the forwarding pointer.

R=mstarzinger@chromium.org
BUG=410912
LOG=N

Review URL: https://codereview.chromium.org/541353003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23722 ce2b1a6d-e550-0410-aec6-3dcde31c8c00