Apply my refactoring changes from r31989.
Restore the dump_stack routine, it's really useful for debugging.
Add ncat_main.c facilities for -L. Currently still with the ugly
o.script name.
Add script loading facilities.
Add null.lua, a filter meant for testing supersocket.
Add connect-mode recv() and send() support.
Revert r32301..r32306.

Committed accidentally.