[network-manager-pptp] doc: update authors

[Lubomir Rintel <lkundrak src gnome org>]

commit cdf7db2db0f73ff49c05bcf549275919ba59194e
Author: Lubomir Rintel <lkundrak v3 sk>
Date:   Mon Aug 31 14:39:49 2015 +0200

    doc: update authors

 AUTHORS |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/AUTHORS b/AUTHORS
index 60e6332..b4c430f 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -1,4 +1,7 @@
 Antony Mee <eemynotna gmail com>
 Tim Niemueller <tim niemueller de>
 Dan Williams <dcbw redhat com>
-
+Lubomir Rintel <lkundrak v3 sk>
+Dan Winship <danw redhat com>
+Michael Biebl <biebl debian org>
+Jiří Klimeš <jklimes redhat com>