edge: Get EGPRS multislot class

The EGPRS MS class ist contained in the MS_RA_capability information.
Its presence indicates, that the MS is able (and willing) to use
EGPRS.

This commit implements basic support for retrieving, storing, and
showing it in the VTY. The information is stored in the MS object.

Sponsored-by: On-Waves ehf
diff --git a/src/pcu_vty_functions.cpp b/src/pcu_vty_functions.cpp
index d2a3641..ce2a006 100644
--- a/src/pcu_vty_functions.cpp
+++ b/src/pcu_vty_functions.cpp
@@ -70,6 +70,7 @@
 	vty_out(vty, "  Coding scheme downlink: CS-%d%s", ms->current_cs_dl(),
 		VTY_NEWLINE);
 	vty_out(vty, "  MS class:               %d%s", ms->ms_class(), VTY_NEWLINE);
+	vty_out(vty, "  EGPRS MS class:         %d%s", ms->egprs_ms_class(), VTY_NEWLINE);
 	vty_out(vty, "  LLC queue length:       %d%s", ms->llc_queue()->size(),
 		VTY_NEWLINE);
 	vty_out(vty, "  LLC queue octets:       %d%s", ms->llc_queue()->octets(),