Update atk to 2.15.3.
Update cairo to 1.14.0.
Update gtk30 to 3.15.3.
Update gnome-themes-standard to 3.15.2.2.
Update gjs to 1.43.3.
Update clutter to 1.21.2.
Add clutter-gst 3.0.0.
Update glib to 2.43.2.
Update glibmm to 2.43.2.
Switch cairo GL option on by default.
Update gtkmm30 to 3.15.3.
Update geocode-glib to 3.15.3.1.
Update vte3 to 0.39.1 and rework gnome-pty-helper port.
Update at-spi2-core to 2.15.3.
Remove the custom gnome error message.

This was probably usefull in the past but the analyser isn't been
maintained for years.
Remove support for GNOME_DESKTOP_VERSION.

It a leftover from when gnome1.4 and gnome2 where in the tree at the same time.
Remove MARCUSCOM_CVS
Update at-spi2-atk to 2.15.3.
Update py-atspi to 2.15.3.
Kill gnomehier off, pkg now does the removing of directories for us.