Previously, if two clients were connected to the same server and one of
them was ahead of the server, the only way to rectify that situation was
for the client to get so far ahead that it stalled, as the server could
only catch up with an ahead client if all clients were ahead. That's
unrealistic. This gives the server the alternate option of demanding
that a client stall. This keeps things nicely in line even with >2
players.
I had previously assumed that if AF_INET6 is defined, IPv6 support was
present. Some psychopathic console SDKs which shall not be named
actually define AF_INET6 but none of the IPv6 structures. As there is
therefore no way to determine whether IPv6 support is present at
preprocessor time, I'm ust assuming that HAVE_SOCKET_LEGACY implies no
IPv6. This means in effect that no consoles get IPv6 support.
Silence some Coverity warnings (including a real memory leak) and be
more careful about checking IPv6 mode (for backwards compatibility with
systems that don't support IPv6 but may run code compiled to expect IPv6)
