linux: sync with upstream harfbuzz

      Upstream changes are:
      fix a few compiler warnings and make the code more exception safe.
      correctly support decomposed forms of two or three part matras
      fix shaping of assamese ra
      fix bug with Malayalam Samvruthokaram.
      add N'Ko support to the arabic shaper
      Post substitutions should apply to the whole indic syllable

Review URL: http://codereview.chromium.org/408013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@32448 0039d316-1c4b-4281-b951-d872f2087c98