It causes mysqlbinlog to not stop after the end of the requested binlog, and instead read
until the end of the last binlog of mysqld (beware of endless loops if you pipe this
into the same mysqld).
I.e. it enables back (at customer's request) what we considered (and I still do)
as BUG#3204, but now with an option instead of being the default behaviour.
The default behaviour is still to stop after the end of the requested binlog,
whether --read-from-remote-server or not.