Allow client to force server to terminate if it exits

This is intended to be used by screen lockers, where the server must
exit if the screen locker does, to avoid a security hole.  As suggested
by Alan Coopersmith, this is implemented using a new flag for the
disconnect mode of the XFixes extension.
9 jobs for DemiMarie-master-patch-34896 in 1 minute and 25 seconds (queued for 6 seconds)
Status Name Job ID Coverage
  Prep
passed container-prep #12034718

00:00:13

 
  Build
passed autotools: [] #12034721

00:00:42

passed autotools: [--enable-legacy] #12034722

00:00:35

passed meson: [] #12034719

00:00:27

passed meson: [-Dlegacy=true] #12034720

00:00:10

 
  Test
passed check evdev keysyms #12034725

00:00:25

passed check versions are in sync #12034726

00:00:20

passed compare meson and autotools #12034724

00:00:27

passed meson from tarball #12034723

00:00:22