Document --inspect-port, and fix the reporting for when it is misused.
The option requires an argument, but when the argument was omitted, the
error message incorrectly reported --inspect-port as being bad, as if
was not supported at all:
% node --inspect-port
node: bad option: --inspect-port
% node --none-such
node: bad option: --none-such
It is now correctly reported as requiring an argument:
% ./node --inspect-port
./node: --inspect-port requires an argument
PR-URL: https://github.com/nodejs/node/pull/12581
Reviewed-By: James M Snell <jasnell@gmail.com>