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
5 files changed