new interfaces code (bug fix + questions)

[tridge at linuxcare.com]

Andrej,

Thanks for the help with the IFREQ code! I don't have access to any
machine that needs it so I couldn't test it.

I've modified your code in a few ways and would appreciate it if you
(and anyone else) could test it:

1) I try to auto-detect whether the size is returned at the start of
   the buffer so we don't need an ifdef. Let me know if you think what
   I've done is valid.

2) I've added new duplicate interface removing code

3) I've changed the call interface

I believe this code should now work on:

Linux 2.*
Solaris 2.*
SunOS4.*
HPUX 10.20
OSF1 V4.0
Ultrix 4.4
SCO Unix 3.2
IRIX 6.*
FreeBSD 3.2
AIX 4.2
ReliantUNIX 5.44

it will probably also work on lots more unixes, especially different
versions of the above. If anyone finds one where none of the 3
possible methods work then please let me know!  Note that I'm now
after reports of failure rather than reports of success.

The new code is at ftp://samba.org/pub/tridge/misc/interfaces.c

> How do you intend to choose the method? I think, that IFCONF must be
> selected if at all possible.

In autoconf I'll try HAVE_IFACE_AIX first, then HAVE_IFACE_IFCONF then
HAVE_IFACE_IFREQ. We need to try AIX first as IFCONF works on AIX but
only gives some of the interfaces.

Cheers, Tridge