Syntax: %bSET <channel> TOPIC <topic|->%b

Causes %C to set the topic on <channel> to <topic>.
Mostly used with TOPICLOCK (%b/msg %C HELP SET TOPICLOCK%b).
Examples:
         %b/msg %C SET #channel TOPIC Welcome to our channel%b
           Causes %C to set the given topic on #channel

         %b/msg %C SET #channel TOPIC -%b
           Clears the topic on #channel
