[CFR] Upgrading base version of our resolver in libc to BIND9

[Hajimu UMEMOTO]

Hi,

I wish to upgrade the base version of our resolver in libc to BIND9's
one.  Since, our resolver is already thread-safe, it doesn't bring in
major benefit for us.  However, it makes chasing updating of BIND9 bit
easier.  Further, new res_n*() functions are used in some applications
these days.

Since, our resolver has many local changes, we cannot simply use
contrib/bind9/lib/bind.  So, I'll import it into lib/libc, then merge
our local changes into it.  I'll separate isc, nameser and resolv
directories from net, as NetBSD did.

Since, res_sendsigned(3) and the friends use MD5 functions, it is hard
to include them without having MD5 functions in libc.  So, I'll not
merge them into libc.

Since, res_update(3) in BIND9 is not binary compatible with our
res_update(3), I'll leave our res_update(3) as is, except some
necessary modifications.
The res_update(3) and the friends are not essential part of the
resolver.  They are not defined in resolv.h but defined in
res_update.h separately in BIND9.  Further, they are not called from
our tree.  So, I'll hide them from our resolv.h, but leave them only
for binary backward compatibility (perhaps, no one calls them).

Since, struct __res_state_ext is not exposed in BIND9, I'll hide it
from our resolv.h.  And, I'll remove global variable _res_ext.  It
breaks binary backward compatibility.  But, since it is not used from
outside of our libc, I think it is safe.

The patches are:

    http://www.imasy.or.jp/~ume/FreeBSD/libc-bind9-7c-20060313.diff.gz
	(for HEAD as of today)
    http://www.imasy.or.jp/~ume/FreeBSD/libc-bind9-6s-20060313.diff.gz
	(for RELENG_6 as of today)

You need to remove some obsolete files.  Please refer the instruction
written in the head of the patch.

Sincerely,

--
Hajimu UMEMOTO @ Internet Mutual Aid Society Yokohama, Japan
ume at mahoroba.org  ume@{,jp.}FreeBSD.org
http://www.imasy.org/~ume/