ggsn: cmdline: no need to specify interface anymore

--gtpnl is now gone, instead you have --gtpkernel that behaves as an on/off
toggle. We full rely on the kernel routing base to select the real device to
transmit.

I have updated ggsn/cmdline.ggo and then run 'gengetopt' to refresh the
automatic code generation for command line options that openggsn uses.
diff --git a/ggsn/cmdline.h b/ggsn/cmdline.h
index 150fb4d..57f5cae 100644
--- a/ggsn/cmdline.h
+++ b/ggsn/cmdline.h
@@ -1,6 +1,6 @@
 /** @file cmdline.h
  *  @brief The header file for the command line option parser
- *  generated by GNU Gengetopt version 2.22.5
+ *  generated by GNU Gengetopt version 2.22.6
  *  http://www.gnu.org/software/gengetopt.
  *  DO NOT modify this file, since it can be overwritten
  *  @author GNU Gengetopt by Lorenzo Bettini */
@@ -95,9 +95,8 @@
   char * loglevel_arg;	/**< @brief Global log ldevel (default='error').  */
   char * loglevel_orig;	/**< @brief Global log ldevel original value given at command line.  */
   const char *loglevel_help; /**< @brief Global log ldevel help description.  */
-  char * gtpnl_arg;	/**< @brief GTP kernel support (default='eth0').  */
-  char * gtpnl_orig;	/**< @brief GTP kernel support original value given at command line.  */
-  const char *gtpnl_help; /**< @brief GTP kernel support help description.  */
+  int gtp_linux_flag;	/**< @brief GTP linux kernel support (default=off).  */
+  const char *gtp_linux_help; /**< @brief GTP linux kernel support help description.  */
   
   unsigned int help_given ;	/**< @brief Whether help was given.  */
   unsigned int version_given ;	/**< @brief Whether version was given.  */
@@ -119,7 +118,7 @@
   unsigned int qos_given ;	/**< @brief Whether qos was given.  */
   unsigned int logfile_given ;	/**< @brief Whether logfile was given.  */
   unsigned int loglevel_given ;	/**< @brief Whether loglevel was given.  */
-  unsigned int gtpnl_given ;	/**< @brief Whether gtpnl was given.  */
+  unsigned int gtp_linux_given ;	/**< @brief Whether gtp-linux was given.  */
 
 } ;
 
@@ -137,6 +136,8 @@
 extern const char *gengetopt_args_info_purpose;
 /** @brief the usage string of the program */
 extern const char *gengetopt_args_info_usage;
+/** @brief the description string of the program */
+extern const char *gengetopt_args_info_description;
 /** @brief all the lines making the help output */
 extern const char *gengetopt_args_info_help[];