MIPS: Added vector-based loadic hydrogen stubs. Not yet callable.

Port r23405 (12573f34)

Original commit message:
The next step is to integrate the use of vector[slot] into the IC
infrastructure so it can do the right thing for a vector-based ic.
Then these stubs can be installed. For now, they immediately bail out
to the miss handler.

BUG=
R=paul.lind@imgtec.com

Review URL: https://codereview.chromium.org/505303002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23422 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Minor-key-ify new LoadICTrampolineStub.

Port r23409 (31a0d5ae)

BUG=
R=paul.lind@imgtec.com

Review URL: https://codereview.chromium.org/503393002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23423 ce2b1a6d-e550-0410-aec6-3dcde31c8c00