The error handling in LLVM for errors has been updated so that errors in
the bitcode stream no longer cause (assertion crashes). This CL applies
the appropriate changes to subzero.

See CL https://codereview.chromium.org/932953002 for changes to error
handling for LLVM.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4002
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/916313004