Draft: community/gnome-common: move from testing
Package gnome-common contains "common development macros for GNOME". The package was moved from "community" to "testing" approx. one year ago because "these are terribly old, no longer supported upstream and are not used by any GNOME project [...]".
To move LightDM greeter slick-greeter to "community", the package gnome-common is also needed in "community" because it's a build dependency for slick-greeter.