This allows for some further hardening against synflooding and connection flooding
where no data is actually sent, as the kernel will simply ignore those connections
(well, as far as the ircd is concerned anyway).
Use RB_SOCKADDR_HAS_SA_LEN instead of SOCKADDR_IN_HAS_LEN
which is only defined inside libratbox.
This fixes creating own sockaddr structs in other programs
using SET_SS_LEN, then passing them to libratbox, on
4.4BSD based systems.
