Ensure that we use ARMv5 instructions on ARMv6 and ARMv7 CPUs.
Review URL: http://codereview.chromium.org/206012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2898 ce2b1a6d-e550-0410-aec6-3dcde31c8c00