ARM32 vector ops - scalarize icmp, fcmp and cast.

This is part of a sequence of patches to quickly fill out vector
support by scalarizing the remaining operations. Later we can work to
generate better code.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4076
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1683153003 .
6 files changed