libcommon: socket: extend make_sock() prototype

This patch extends the make_sock() prototype so you can fully set
the fields priv_nr and data of the bsc_fd structure.

This is the first step to get rid of the internal make_sock()
implementation that ipaccess-proxy uses.

This patch includes a minor cleanup to pass INADDR_ANY instead
of zero, if you do not want to bind the socket to one specific
address.
diff --git a/openbsc/src/libgb/gprs_ns_frgre.c b/openbsc/src/libgb/gprs_ns_frgre.c
index 98b1ad6..85019e1 100644
--- a/openbsc/src/libgb/gprs_ns_frgre.c
+++ b/openbsc/src/libgb/gprs_ns_frgre.c
@@ -292,7 +292,7 @@
 		return 0;
 
 	rc = make_sock(&nsi->frgre.fd, IPPROTO_GRE, nsi->frgre.local_ip,
-			0, nsfrgre_fd_cb);
+			0, 0, nsfrgre_fd_cb, NULL);
 	if (rc < 0) {
 		LOGP(DNS, LOGL_ERROR, "Error creating GRE socket (%s)\n",
 			strerror(errno));