SNDCP: add V.42bis data compression functionality

 - Add compression control for V.42bis Add code to handle compression
   (gprs_sndcp_dcomp.c/h)
 - Add Adjustments in SNDCP
 - Add VTY commands

Change-Id: I6d36cbdf2f5c5f83ca9ba57c70452f02b8582e7e
diff --git a/openbsc/src/gprs/sgsn_main.c b/openbsc/src/gprs/sgsn_main.c
index 9f3260d..fb5b6d5 100644
--- a/openbsc/src/gprs/sgsn_main.c
+++ b/openbsc/src/gprs/sgsn_main.c
@@ -299,6 +299,11 @@
 		.description = "RFC1144 TCP/IP Header compression (SLHC)",
 		.enabled = 1, .loglevel = LOGL_DEBUG,
 	},
+	[DV42BIS] = {
+		.name = "DV42BIS",
+		.description = "V.42bis data compression (SNDCP)",
+		.enabled = 1, .loglevel = LOGL_DEBUG,
+	}
 };
 
 static const struct log_info gprs_log_info = {