Define NOMINMAX across the entire project.

This fixes the standalone build on Windows and matches Chromium.

Change-Id: I194f53e0a610c5ae9cef53c826b22f7bded5f357
Reviewed-on: https://boringssl-review.googlesource.com/4201
Reviewed-by: Adam Langley <agl@google.com>
3 files changed