MIPS: Create AllocationSite objects, pointed to by AllocationSiteInfo.

Port r15545 (8cf04c4)

Original commit message:
This creates a platform where we can do additional things with allocation sites,
other than just aid in reducing array transitions.

BUG=

Review URL: https://codereview.chromium.org/18089025
Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15561 ce2b1a6d-e550-0410-aec6-3dcde31c8c00