As with Arm, the kernel defines this stuff, but bionic lib does not.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9298016
Patch from Paul Lind <plind44@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10556 ce2b1a6d-e550-0410-aec6-3dcde31c8c00