Better handling of "no valid path".

- Fixed error message.
- Try to prevent marking an incomplete path.
- Prevented most of "Use of uninitialized value"
Better parsing of simple protocols.
Print 'unknown' as IP address of autointerface.
Added '-quiet' option
(c) 2013
Caching improves performance of gen_reverse_rules
v3.038

 - print-group no longer aborts when printing IP address of auto interface,
   but prints "unknown".
 - print-group now supports option "-quiet".
 - Better error handling.
 - Improved runtime performance when generating reverse rules
   for stateless routers.