X87: Make KeyedLoads from a sloppy arguments array use a handler.

port r24120.

original commit message:
   Make KeyedLoads from a sloppy arguments array use a handler.
   Before, a custom stub was installed

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/594773002

Patch from Chunyang Dai <chunyang.dai@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24128 ce2b1a6d-e550-0410-aec6-3dcde31c8c00