When doing file verification, tftp needs to be able to handle multiple
open files concurrently.
We also need tftp_stat() to provide useful values for st_dev and st_ino.
Allow an architecture to define NETPROTO_DEFAULT.
The default is NET_NFS for backwards compatability.
In net_parse_rootpath() fix parsing of
<scheme>://<ip>[:<port]/<path>
and ensure we return INADDR_NONE unless we successfully
parsed an addr, so we don't end up clobbering rootip obtained
from bootp().
In install() if proto has not been determined, but
netproto is NET_TFTP set proto to tftp_fsops.
Put a common DEBUG_PRINTF impl in stand.h so we can over time have
more consistent approach to debugging bits of the loader.
Sponsored by: Juniper Networks, Inc.