[GTK] cleanup GtkWebKitMini.cs
[GTK] update libwebkitgtk reference and dllmaps
to enable plain Gtk.WebView support on windows and mac
(thx@ lytico)
[GTK] stop using deprecated libwebkitgtk api
(thx@ lytico)
[Samples] fix WebView url filter example
(relative urls produced an exception)
Merge branch 'extend-webview' of git://github.com/sevoku/xwt into sevoku-extend-webview

Conflicts:
	Xwt.Gtk/Xwt.GtkBackend/GtkInterop.cs
Merge branch 'sevoku-extend-webview'