Create new 'gprs-sgsn' branch on top of 'gprs-conf'

This branch contains the partial SGSN/GGSN implementation that
was originally developed as part of the gprs branch.
diff --git a/openbsc/src/vty_interface_cmds.c b/openbsc/src/vty_interface_cmds.c
index 671351e..efcd654 100644
--- a/openbsc/src/vty_interface_cmds.c
+++ b/openbsc/src/vty_interface_cmds.c
@@ -142,7 +142,7 @@
 }
 
 /* FIXME: those have to be kept in sync with the log levels and categories */
-#define VTY_DEBUG_CATEGORIES "(rll|cc|mm|rr|rsl|nm|sms|pag|mncc|inp|mi|mib|mux|meas|sccp|msc|mgcp|ho|db|ref)"
+#define VTY_DEBUG_CATEGORIES "(rll|cc|mm|rr|rsl|nm|sms|pag|mncc|inp|mi|mib|mux|meas|sccp|msc|mgcp|ho|db|ref|gprs)"
 #define VTY_DEBUG_LEVELS "(everything|debug|info|notice|error|fatal)"
 DEFUN(logging_level,
       logging_level_cmd,