Send CR/NUL for <Enter> rather than CR/LF. Although the Telnet spec (RFC854)
requires that either combination be accepted as a single "new line" character,
some Telnet servers treat CR and LF as separate input characters and do weird
things (e.g. treat the LF as a second <Enter> key or <^J> or invalid input).
If we ever come across a Telnet server that does something weird with CR/NUL
(and works better receiving CRLF) then perhaps we'll need a configuration
option. Hopefully not. Of course, in binary mode, none of this applies.