(uintN_t)1 << M has undefined behavior when M >= N.  For example, the
following:

    shift = 64;
    value = 1 << shift;

Gives a value of 1 (instead of the arithmetically expected 0) on (some?)
Intel CPUs.

Bug: None
Change-Id: I5fbb01eff812a62eb778474cec25a25b80052bac
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2269857
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>