std::to_ullong is c++11, failing on Mac.

BUG=angleproject:1040

This reverts commit 37a9e712.

Change-Id: I5cecd1fe95b889feffb556f67d082cec585256f4
Reviewed-on: https://chromium-review.googlesource.com/290211Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>