WebKit external dependency update

[Alp Toker <alp atoker com>]

Hi,

WebKit/GTK+ now has AT-SPI accessibility support using ATK as requested 
by the Yelp developers, which was laid out as a requirement for the 
external dependency. We hooked it up to support some ARIA capabilities 
and worked to improve keyboard navigation, features that were listed as 
desirables by the GNOME accessibility team. There's also now some 
support for accessible text editing via AT-SPI in preparation for the 
expected migrations from GtkHTML. Accessibility work will be ongoing in 
trunk but I believe we're ready for testing as part of the development 
release.

Are we ready to get this on the external dependency list for 2.23.3?