[Gtk3] reenable GetTooltipContext for Gtk3
[Gtk3] remove useless Gtk3 check
[Gtk] add major version check (support Gtk3)
[Gtk] use version detection for toolkit features
[Gtk3] fix build on windows
 * don't provide package names in project file
[Gtk3] complete Xwt-Gdk.RGBA-Xwt conversion
[Gtk3] fix libwebkitgtk-3 import names
Merge pull request #390 from sevoku/gtk3-fixes

[Gtk] Fix Gtk2/3 version detection + small Gtk3 fixes