Suppress C4334 32/64 bit shift warning for harfbuzz on win

Suppress the C4334 32/64 bit shift warning on windows to allow it to be
compiled on windows x64.

TBR=behdad@chromium.org
BUG=

Review URL: https://codereview.chromium.org/74443002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235478 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235478