mgcp_client: add function to generate e1-endpoint names

mgcp_client.h offers functions to generate endpoint names for wildcarded
request. This is used in osmo-bsc, lets now also add a function that can
generate e1-endpoint names.

Change-Id: Iec35b5bae8a7b07ddb3559f7114a24dcd10e8f14
Related: OS#2547
diff --git a/include/osmocom/mgcp_client/mgcp_client.h b/include/osmocom/mgcp_client/mgcp_client.h
index 32bd87b..d4dd2d9 100644
--- a/include/osmocom/mgcp_client/mgcp_client.h
+++ b/include/osmocom/mgcp_client/mgcp_client.h
@@ -137,6 +137,8 @@
 
 const char *mgcp_client_endpoint_domain(const struct mgcp_client *mgcp);
 const char *mgcp_client_rtpbridge_wildcard(const struct mgcp_client *mgcp);
+const char *mgcp_client_e1_epname(void *ctx, const struct mgcp_client *mgcp, uint8_t trunk_id, uint8_t ts,
+				  uint8_t rate, uint8_t offset);
 
 /* Invoked when an MGCP response is received or sending failed.  When the
  * response is passed as NULL, this indicates failure during transmission. */