'RELENG_7_0_0_RELEASE'.

This commit was manufactured to restore the state of the 7.0-RELEASE image.

  expose them to outside of libc.
- make netdb functions NSS friendly.

Reviewed by:	arch@ and current@ (no objection)

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

Since, res_update(3) in BIND9 is not binary compatible with our
res_update(3), res_update(3) is leaved 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 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 hide it
from our resolv.h.  And, global variable _res_ext is removed.  It
breaks binary backward compatibility.  But, since it is not used from
outside of our libc, I think it is safe.

Reviewed by:	arch@ (no objection)

  netent.
- Change 1st argument of getnetbyaddr() to an uint32_t on 64 bit
  arch as well to confirm to POSIX-2001.

These changes break ABI compatibility on 64 bit arch.
There is similar padding issue for ai_addrlen of struct addrinfo.
However, it is leaved as is for now.

Discussed on:	arch@, standards@ and current@
X-MFC after:	never

  RFC 2553.  In XNS5.2, and subsequently in POSIX-2001 and RFC
  3493, it was changed to a socklen_t.  And, the n_net of a
  struct netent used to be an unsigned long integer.  In XNS5,
  and subsequently in POSIX-2001, it was changed to an uint32_t.
  To accomodate for this while preserving ABI compatibility with
  the old interface, we need to prepend or append 32 bits of
  padding, depending on the (LP64) architecture's endianness.
- Correct 1st argument of getnetbyaddr() to uint32_t on 32
  bit arch.  Stay as is on 64 bit arch for ABI backward
  compatibility for now.

Reviewed by:	das, peter
MFC after:	2 weeks

I believe have made all of libc .c's as consistent as possible.