AF_LOCAL on Linus *should* be available

[derrell at samba.org]

derrell at samba.org writes:

> Running "configure.developer" in the SAMBA_3_0 tree, I noticed that it
> displays:
>
>   checking for AF_LOCAL socket support... no
>
> All four of AF_LOCAL, AF_UNIX, PF_LOCAL, PF_UNIX are defined in
> <linux/socket.h>.  Since I'm not a follower of the black art of "configure"
> scripting, maybe someone who is can look and see why it thinks that AF_LOCAL
> is not available.

It seems that there is no test for whether <sys/un.h> exists, and thus setting
HAVE_SYS_UN_H never occurs.  The test for AF_LOCAL uses tests/unixsock.c which
uses that manifest constant to determine whether to include <sys/un.h>.  The
program does not compile without that include file, thus the test fails.

Derrell