Add function _dbus_get_peer_pid_from_tcp_handle() which returns pid and sid from...

Add function _dbus_get_peer_pid_from_tcp_handle() which returns pid and sid from tcp connection peer.

This function is called by _dbus_read_credentials_socket() to fetch client credentials.

Because Wine is used to check cross compiled dbus for windows, in calls to GetExtendedTcpTable()
we use table class TCP_TABLE_OWNER_PID_ALL instead of TCP_TABLE_OWNER_PID_CONNECTIONS.
This class is the only one which is available since wine 1.5.3.

https://bugs.freedesktop.org/show_bug.cgi?id=61787
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>