Remove core/platform/text/{mac, win}

These directories only exist to contain LocaleMac and LocaleWin, respectively.
We can just move those files to be next to LocaleICU.

R=adamk@chromium.org

Review URL: https://codereview.chromium.org/25674007

git-svn-id: svn://svn.chromium.org/blink/trunk@158838 bbb929c8-8fbe-4397-9dbb-9b2b20218538