Now that warnings were almost all removed, let's enable zero-warning
via -dW. All tests were adjusted, but two:
- mcli/mcli_start_progs.vtc:
the programs section currently cannot be silenced
- stats/stats-file.vtc:
the warning comes from the stats file itself on comment lines.
All other ones are now OK.
No less than 30 tests were missing timeouts, preventing them from being
started with zero-warning. Since they were not supposed to trigger, they
have been set to 30s so as never to trigger, and now they do not produce
any warning anymore.