GNOME Boxes QEMU Frontend App Gets Ready for the GNOME 3.20, Adds VNC Fixes

There are mostly bug fixes and performance improvements in the Release Candidate build of GNOME Boxes 3.20, and among the most important ones we can mention two crashes related to the VNC (Virtual Network Computing) support, a session libvirt-related issue that made the software to quite when the connection to the default broker failed.