Generally tried to make them more reliable and execute quicker.
They all now load the listen script as a trick to make sure input
sources are fully read, but also terminate() at appropriate times
so that they don't take more time than needed. They're also all
serialized with the 'comm' group so listening on a port doesn't
interfere with the communication tests.
This do not have to be present in the input file and are marked as &optional in the record description.
Those can e.g. be used to create field values on the file in a predicate while reading a file - example:
Input::add_table([$source="input.log", $name="input", $idx=Idx, $val=Val, $destination=servers,
$pred(typ: Input::Event, left: Idx, right: Val) = { right$notb = !right$b; return T; }
