network(), syslog() sources: add $PEERIP and $PEERPORT macros

[MrAnno]

The $PEERIP and $PEERPORT macros always display the address and port of the direct sender.
In most cases, these values are identical to $SOURCEIP and $SOURCEPORT.
However, when dealing with proxied protocols, $PEERIP and $PEERPORT reflect the proxy's address and port,
while $SOURCEIP and $SOURCEPORT indicate the original source of the message.