Add strnchr() to str.c
Improve new "config dump" command

No more SEGV.  Omits invalid (default) values.  Logs unconditional DEBUG
output, to be removed before merging into development.  Still missing
cf_cmp_ functions to prune out default values.

Improved config Object Model iterator logic to barf on internal NULL
nodes.
Fix bugs in interface pattern list parsing

Treat empty pattern list as invalid.

Fix bug in legacy interface parser: was not handling asterisk wildcards
'*' properly.
Fix some config schema declarations

Replace 'int' representation with 'uint32_nonneg', so that default value
of -1 is out of reach of parser.