Consider making Ncat -w act as a listen timeout in server mode

[dmiller-nmap]

Currently, Ncat's -w option is a connect timeout, separate from the -i idle timeout, which only works in connect/client mode. We should consider whether this should be extended to be a listen timeout in server mode, since we removed that aspect of -i.

Considerations:

• Do other netcats (traditional & OpenBSD) have such a feature? Does it have a consistent option letter? If so, then we should use that instead.
• How do other netcats handle the -w option in listen/server mode? IIRC, it is used as an idle timeout only. But if others are consistent, we should be consistent also. If the others disagree with each other, we may choose either side or something different.
• Does the existing documentation contradict this proposal? We will have to change the documentation, but we should be cautious about a change that results in an opposite meaning from existing documentation.

[dmiller-nmap]

Related: #798 (-w in connect mode has different behavior)

[dmiller-nmap]

Traditional netcat uses -w as a universal timeout for connect, accept (listen), and idle connections. OpenBSD netcat uses -w for connect timeout and idle connections, but will block on accept without any timer.

Our existing documentation is out-of-date in that it states Ncat in listen mode does not support either -i or -w for timing options. This needs to be updated. Refer to the Ncat to netcat Compatibility Guide for current compatibility guidance.