webkit-gtk: Update www/webkit-gtk to 2.22.3

Changes:
WebKitGTK+ 2.22.3
=================
  - Many improvements and fixes for video playback with media source
    extensions (MSE), which improve the user experience across the board,
    and in particular for playback of WebM videos.
  - Fix a memory leak during media playback when using playbin3.
  - Fix portions of Web views not being rendered after resizing.
  - Fix Resource Timing reporting for <iframe> elements.
  - Fix the build with the remote Web Inspector disabled.
  - Fix the build on ARMv7 with NEON extensions.
  - Fix several crashes and rendering issues.

(leot)