WebKitGTK+ 2.21.1 released!

This is the first development release leading toward 2.22 series.

Add initial JavaScriptCore GLib API.
Use JavaScriptCore GLib API in WebKit layer and deprecate most of the DOM bindings API as well as methods using the JavaScriptCore C API.
Switch to use complex text code path unconditionally.
Properly close the connection to the Wayland nested compositor in the WebProcess.
Implement support for Graphics ARIA roles.
Add playbin3 support to GStreamer media backend.
Fix a deadlock when destroying the media player in non accelerated compositing mode.
Fix several crashes and rendering issues.

Thanks to all the contributors who made possible this release.