WebKitGTK+ 2.17.4 released!

This is a development release leading toward 2.18 series.

Add API to allow overriding popup menus.
Add kinetic scrolling support.
Improve theme rendering performance when using GTK+ >= 3.20.
Improve error message when webkit_web_view_run_javascript() fails due to a JavaScript exception.
Fix artifacts when rendering large images.
Fix blob downloads.
Fix web process deadlock when seeking youtube videos.
Fix alpha premultiplying when using cairo to draw the video frames.
Fix web process deadlock when closing the remote inspector frontend.
Update several web inspector icons.
Fix several crashes and rendering issues.
Translation updates: Spanish.

Thanks to all the contributors who made possible this release.