Virtually every system that supports TCP/IP and sockets
(including Linux, AIX, Winsock, and *BSD) has the constant
INADDR_NONE defined in <netinet/in.h>.  This symbol represents
the error value returned by the Standard inet_addr() function.
(The Open Group standards refer to this function as returning
(in_addr_t)-1 on error.)

Solaris, though, lacks this symbol, and instead defines it in
many different places throughout the current ON source base,
and likely in other gates as well.

Though inet_addr() is an old and mostly "deprecated" function,
failing to define this symbol serves only to increase the
difficulty in porting to Solaris.

This project adds INADDR_NONE to <netinet/in.h> as a Stable
interface.  A patch/micro release binding is asserted.

The man page for inet(3SOCKET) will be updated to indicate
that INADDR_NONE is returned by inet_addr() and inet_network()
on error, and that (per the standards) this value is
equivalent to (in_addr_t)-1.

The INADDR_NONE symbol will be visible when INADDR_LOOPBACK is
visible, which currently means "always."  It's not defined by the
standard, but all INADDR_* symbols are reserved in the standard
for definition by this file.