New upstream release

- Update debian/copyright
- Update disabled ostree-boot packaging for new systemd generator
- Add new ABI to symbols file

debian/ostree-boot.install

@@ -1,5 +1,6 @@
 etc/dracut.conf.d/ostree.conf
 etc/grub.d/15_ostree
+lib/systemd/system-generators/ostree-system-generator
 lib/systemd/system/ostree-prepare-root.service
 lib/systemd/system/ostree-remount.service
 usr/lib/dracut/modules.d/98ostree