nmsgtool manpage requests

[reedjc]

This ticket is for adding some missing documentation to the nmsgtool manual:

-B --byterate

-X --readxchan

--readif (optional for -i)

-D --daemon

-P --pidfile

-U --username

-v --version

--unbuffered

Maybe while there alphabetize the options?

Also document the environment variables:

NMSG_BPF environment variable sets c->bpfstr (same as -b or --bpf)

NMSG_KICKER sets c->kicker (same as -k or --kicker)

These both override corresponding command line options.

NMSG_MSGMOD_DIR overrides the default directory for finding message modules. Later this could be in a nmsg.3 manual.

And either put into this manual the base environment variable settings. (I am fine with doing a new man page for this but since these are builtin, same manual is fine with me for now. Or it could be moved to a new nmsg.3 manual):

DNSQR_CAPTURE_QR

DNSQR_CAPTURE_RD

DNSQR_ZERO_RESOLVER_ADDRESS

DNSQR_STATE_TABLE_MAX

DNSQR_QUERY_TIMEOUT

DNSQR_AUTH_ADDRS

DNSQR_RES_ADDRS

DNSQR_FILTER_QNAMES_INCLUDE

DNSQR_FILTER_QNAMES_EXCLUDE

[reedjc]

Also manpage has -I --p -text and -I --p -json
but should be -I -p text and -I -p json