release: bump version to 1.8.28

6 jobs for 1.8.28 in 20 minutes and 35 seconds
latest
Status Name Job ID Coverage
  Build
passed fedora28_dist #620932

00:07:33

 
  Test
passed centos7 #620937

00:13:00

passed fedora_autotools_full #620936

00:10:46

passed fedora_autotools_minimal #620935

00:04:05

passed fedora_meson_full #620934

00:10:27

passed fedora_meson_minimal #620933

00:08:17