Add some locking when outputting logs from multiple threads
Add some locking when outputting logs from multiple threads

kalev/appstream-glib,superm1/appstream-glib,hughsie/appstream-glib,mitya57/appstream-glib,ximion/appstream-glib,ximion/appstream-glib,ikeydoherty/appstream-glib,ximion/appstream-glib,kalev/appstream-glib,mitya57/appstream-glib,superm1/appstream-glib,ikeydoherty/appstream-glib,hughsie/appstream-glib,hughsie/appstream-glib