send_gmcp() - send a GMCP message
void send_gmcp( string message );
Sends a GMCP 'message' for this_object() to the user's client.
For payload formatting information see: http://www.gammon.com.au/gmcp,
https://github.com/keneanung/GMCPAdditions
Note: send_gmcp() should only be called from within a user object.
gmcp_enable(4), gmcp(4), has_gmcp(3)