CPP: Fix compilation error on Windows.
CPP: Fix compilation error on Windows.

This appears when the library is built in Chromium.

R=lararennie@google.com

Review URL: https://codereview.appspot.com/10286044
nyaruka/libphonenumber,nyaruka/libphonenumber,nyaruka/libphonenumber,nyaruka/libphonenumber