Use the system stdint.h on Windows.

This is now possible since VC2010 and later provide a stdint.h. VC2008
has been deprecated for building Chromium (and Skia) for a full year now.

There are a number of stdint.h implementations in the codebase, some of
which hide others, and most of which are not complete (Skia in particular
requires uintmax_t which this one did not provide).

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/26358014

git-svn-id: svn://svn.chromium.org/blink/trunk@159684 bbb929c8-8fbe-4397-9dbb-9b2b20218538