ASCI: Add simple implementation of Group Call Register

This is a built-in data structure to store and handle voice group calls.

The GCR will be used by VGCS/VBS call control.
 (Chg-Id: I9947403fde8212b66758104443c60aaacc8b1e7b)

The GCR will be used by VTY code.
 (Chg-Id: I5bd034a62fc8b483f550d29103c2f7587198f590)

Change-Id: Ia74a4a865f943c5fb388cd28f9406005c92e663e
Related: OS#4854
diff --git a/src/libmsc/Makefile.am b/src/libmsc/Makefile.am
index fba7b53..c4e134c 100644
--- a/src/libmsc/Makefile.am
+++ b/src/libmsc/Makefile.am
@@ -76,6 +76,7 @@
 	sgs_iface.c \
 	sgs_server.c \
 	sgs_vty.c \
+	asci_gcr.c \
 	$(NULL)
 
 if BUILD_IU