Migrate to libhandy 1

As of August 7, a first beta release is available.

The code to build can now be downloaded from gnome.org.

A migration guide is available, just as packages for Debian.

added T: task label

mentioned in commit 3bb182e1

mentioned in merge request !49 (merged)

mentioned in commit 46c8e3c0

mentioned in commit a01e28b5

mentioned in commit 01cbca1a

mentioned in commit 6b422b0b

mentioned in commit 502705f4

closed via merge request !49 (merged)