Merge branch 'master' into dev

Conflicts:
	libmate-desktop/mate-bg.c
build libmate-desktop-3.so for gtk3 runtime. drop mate-desktop-2.0-uninstalled.pc.in
Merge branch 'libmate-desktop-3.so'
Merge branch 'master' into dev
Merge branch 'dev' of github.com:dnk/mate-desktop into dev

Conflicts:
	libmate-desktop/mate-bg.h