gprs_ns: Allow to set the DSCP for the UDP socket.

Allow to tag the NS service with a custom DSCP.
diff --git a/src/gb/Makefile.am b/src/gb/Makefile.am
index 8b7473d..af45720 100644
--- a/src/gb/Makefile.am
+++ b/src/gb/Makefile.am
@@ -1,3 +1,6 @@
+# FIXME: LIBVERSION adjustments required for next version
+#  ABI of gprs_ns structure changed by adding DSCP.
+#
 # This is _NOT_ the library release version, it's an API version.
 # Please read Chapter 6 "Library interface versions" of the libtool documentation before making any modification
 LIBVERSION=2:0:0