Log Message:
Update www/webkit-gtk to 2.12.4

Changes:
WebKitGTK+  2.12.4
==================
 - Fix performance in accelerated compositing mode with the modesetting intel
   driver and DRI3 enabled.
 - Reduce the amount of file descriptors that the Web Process keeps open.
 - Fix Web Process deadlocks when loading HLS videos.
 - Make CSS and SVG animations run at 60fps.
 - Make meter elements accessible.
 - Improve accessibility name and description of elements to make it more
   compatible with W3C specs and fix several bugs in which the accessible
   name of objects was missing or broken.
 - Fix a crash when running windowed plugins under Wayland.
 - Fix a crash at process exit under Wayland.
 - Fix several crashes and rendering issues.
 - Translation updates: German.
 - Security fixes: CVE-2016-4622, CVE-2016-4624, CVE-2016-4591, CVE-2016-4590.