[Feature] Update LOGOUT to accept an exit status code in addition to FAST flag

[nbriggs]

Update LOGOUT to accept a STATUS value as an additional argument that can be passed to the LISPFINISH subr to provide a value for the exit status of the process.

The OS exit(status) arguments accepted are typically 0..255, with 0 indicating success and 1 indicating failure and other values having no defined interpretation.

Having an additional argument to LOGOUT will keep the FAST flag (saving or discarding vmem state before exit) independent of the exit status.

[nbriggs]

Closed by PR Interlisp/maiko#525