Macro redefinition is for INT8_MIN, etc. which are generated by flex.
VS doesn't define __STDC_VERSION__ as >= C99 because it's still only
partial support in VS2015.

Fix a float->int conversion narrowing warning.

Change-Id: I5232eb23426eaf584218137c068e14d74119a1ef
Reviewed-on: https://chromium-review.googlesource.com/268821Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Scott Graham <scottmg@chromium.org>