Update type definitions in ppapi/lib/gl/include/KHR/khrplatform.h

This fixes building PPAPI examples on Win 64 after (I believe) r242740.

See also: third_party/khronos/KHR/khrplatform.h

BUG=326382
R=bajones@chromium.org, bbudge@chromium.org

Review URL: https://codereview.chromium.org/125013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243248 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243248