Add support for saturation instruction (ARMv6 or above).
The byte array clamping code has been updated accordingly.

Review URL: http://codereview.chromium.org/3036008/show

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5106 ce2b1a6d-e550-0410-aec6-3dcde31c8c00