Poll update

See merge request !116

Still needs updates in services_thread(), CGI stuff in websrvr.c,
and sbbs_t::external()

Found by digging through headers... Apple doesn't document this.

Just some more macOS silliness.

Sometimes the comment wasn't redrawn.
Also, remove configurable mouse actions stuff, not implemented in
13 years, I suspect I'll never do it.

While they both delete a character, delete at the end of a line will
move the next line up instead of moving this line up.

Fixes #243

Just in case it was read as a string (e.g. had a ; comment following the value)

caused it to be represented as JS string rather than number causing an issue
with login.js:
Node 1 terminal not detected, reducing inactivity hang-up timeout to 0 seconds

Redraw map before returning to startma/startma1

There's likely an ass-ton of these though.

Also check bbs.online for sbbs input.

Synchronet goes boom.

When a players map is set, it automatically triggers a player record
write.  When a new player is being created, the map is set before
the player is added via @addchar.

This attempted to write record number undefined in the player file,
which threw an exception.  Since exceptions are being caught, logged,
and ignored, this did not cause a problem, but did log an error when
it wasn't necessary.

This should never actually be done though since the map would be
completely empty.

Prevents a who's online list from aborting early when it encounters
and invalid player record.

Used by gcc in warnings.

If a '\r' is the last thing in the previous receive buffer.

Not all implementations set POLLHUP when a TCP socket is half-closed.

Was returning disconnected when it wasn't at times.

This likely unbreaks the things.

A socket isn't bad just because there was no incoming connections. :D

This won't impact Synchronet as it has a separate signal handling
thread, but we still need to behave properly for processes that
don't.  I'm also saying that ENOMEM does not indicate a disconnection,
though it may be better to pretend it was disconnected...

socket_readable() returns TRUE if recv() will not block if called
on the specified socket.

socket_writable() returns TRUE if send() will not block if called
on the specified socket.

socket_recvdone() returns TRUE if all data has been recv()ed an
the socket is closed.

"will not block" includes "will return an error".

This matches the three main use-cases for select() of a single socket
in Synchronet.

Use them in the SyncTERM RLogin stuff so they can be tested easily.