* migrate the WHO struct to strbuf

* migrate the WHO struct to strbuf
* add SVPUTBuf() which can handle strbuffers
* register the ITERATOR("WHO")
* provide tokens via the who iterator func: WHO:NAME, WHO:ROOM, WHO:HOST, WHO:REALROOM, WHO:REALHOST, WHO:LASTACTIVE, WHO:SESSION, WHO:IDLE, WHO:NSESSIONS
* some fixes to do_template, and the whole other stuff