socket: Introduce API osmo_sock_init2_multiaddr()

This API will be used by libosmo-netif's osmo_stream for SCTP sockets,
which in turn will be used by libosmo-sccp to support multi-homed
connections.

Related: OS#3608
Change-Id: Ic8681d9e093216c99c6bca4be81c31ef83688ed1
diff --git a/debian/control b/debian/control
index 07163da..6c9cfae 100644
--- a/debian/control
+++ b/debian/control
@@ -15,6 +15,7 @@
                libpcsclite-dev,
                pkg-config,
                libtalloc-dev,
+               libsctp-dev,
                python (>= 2.7.6)
 Standards-Version: 3.9.8
 Vcs-Git: git://git.osmocom.org/libosmocore.git