This patch enables many crosstests for ARM32. Very limited vector
support is implemented (essentially, whatever it takes to compile the
.ll files contain vector operations.)

Atomics as well as vector crosstests are still disabled.

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

Review URL: https://codereview.chromium.org/1359193003 .