Be explicit about not wanting a trigraph.

Both cl.exe and clang-cl don't use trigraphs on Windows by default, but
clang still warns about them.  Since the standard does include trigraphs,
fix the code to not (accidentally) include a trigraph rather than siliencing
the warning.

BUG=82385

Review URL: https://codereview.chromium.org/822813003

Cr-Commit-Position: refs/heads/master@{#309526}
1 file changed