Rename OpenGGSN to OsmoGGSN

Osmocom has maintained this program since about 7 years now, while
the original author / copyright holder has completely disappeared.

With the introduction of Osmocom-style CTRL and VTY interfaces,
the way how the program is used and configured has substantially
changed.  In order to avoid confusion in terms of configuration file
format etc, let's rename it to OsmoGGSN.

Change-Id: I2da30f7d4828e185bfac1a4e2d8414b01cbe4f9d
diff --git a/gtp/gtp.c b/gtp/gtp.c
index 87ab075..27a07b1 100644
--- a/gtp/gtp.c
+++ b/gtp/gtp.c
@@ -1,6 +1,8 @@
 /* 
- *  OpenGGSN - Gateway GPRS Support Node
+ *  OsmoGGSN - Gateway GPRS Support Node
  *  Copyright (C) 2002, 2003, 2004 Mondru AB.
+ *  Copyright (C) 2010-2011, 2016-2017 Harald Welte <laforge@gnumonks.org>
+ *  Copyright (C) 2015-2017 sysmocom - s.f.m.c. GmbH
  * 
  *  The contents of this file may be used under the terms of the GNU
  *  General Public License Version 2, provided that the above copyright