QNativeSocketEngine Windows: bring bind() in line with Unix

QNativeSocketEngine Windows: bring bind() in line with Unix

The IPv4+IPv6 dual stack code that has been in Qt since 5.0 has been
giving test failures for tst_qudpsocket: some binds that shouldn't
succeed do succeed. Instead, copy the core code from the Unix version so
the two OSes will behave the same way.

The one difference in behavior between Windows and Unix is that on Unix
you can bind an IPv4 address to a multicast IP and on Windows you can't.
So I left the "correction" that was in the original code, but I'm unsure
if it is the right thing to do. Are people expecting to join the
multicast group this way?

Change-Id: Iee8cbc07c4434ce9b560ffff13caa1c3d5a7e8fd
Reviewed-by: Richard J. Moore <rich@kde.org>