Subzero. X8664. Fixes various small bugs.

These were all pointed out by the llvm test suite, the gcc torture
tests, and the scons tests.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4077
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1631383002 .
4 files changed