MAINTAINERS: New section "Incompatible changes", copy libvir-list

Libvirt developers would like to be copied on patches to qemu-doc
appendix "Deprecated features".  Do them the favor.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180716073226.21127-3-armbru@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

MAINTAINERS

@@ -2194,6 +2194,10 @@ M: Daniel P. Berrange <berrange@redhat.com>
 S: Odd Fixes
 F: docs/devel/build-system.txt
 
+Incompatible changes
+R: libvir-list@redhat.com
+F: qemu-deprecated.texi
+
 Build System
 ------------
 GIT submodules