Look up XMPP SRV records (library)

 All functions return []SRV with SRV being the following struct:
 .
 type SRV struct {
         Type string
         Target string
         Port uint16
         Priority uint16
         Weight uint16
 }
 .
 Type is either xmpp-client, xmpps-client, xmpp-server or xmpps-server.
 .
 The functions LookupXmppServer, LookupXmppsServer, LookupXmppClient
 and LookupXmppsClient` are called with the server name and return the
 respective SRV records.
 .
 The function LookupClient and LookupServer are also called with the
 server name but return xmpp and xmpps SRV records ordered by priority
 and weight.