AUTHORS: add Pino Toscano as a maintainer

$ git log --committer=ptoscano@redhat.com --pretty=oneline | wc -l
11
Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

AUTHORS.in

@@ -27,6 +27,7 @@ Michal Prívozník <mprivozn@redhat.com>
 Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
 Pavel Hrdina <phrdina@redhat.com>
 Peter Krempa <pkrempa@redhat.com>
+Pino Toscano <ptoscano@redhat.com>
 Richard W.M. Jones <rjones@redhat.com>
 Roman Bogorodskiy <bogorodskiy@gmail.com>