everything gets written immediately, but you can make it wait until
there's specified amount of data in buffer or write once in a hour or
so. Useful for people who want to keep hard disk at sleep at nights but
still want to log.
/SET write_buffer_mins, /SET write_buffer_kb: When to flush buffer.
/FLUSHBUFFER: Flush the buffer immediately
git-svn-id: http://svn.irssi.org/repos/irssi/trunk@1201 dbcabf3a-b0e7-0310-adc4-f8d773084564
