subs: Oops when a telegram doesn't end with a newline

subs: Oops when a telegram doesn't end with a newline

Telegrams should always end with a newline.  The common cause for a
missing newline is misuse of wu() to print partial lines.  Almost
always works, as the read command merges telegrams arriving in quick
succession.  But if the telegrams are more than five seconds apart
(clock jumped somehow), we get a telegram header in the middle of a
line.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>