Fix for 64-bit machines.

I am almost sure this is the cause for
BUG#1381 [Opn]: Bug in replication on HP-UX 64 bit binaries?
BUG#1256 [CRp]: Replication slave fails to connect to master in 64-bit version (Solaris)
The reason why I think it's wrong is that the normal client code has 
uint32 ip_addr.
(of course on 32-bit machines it does not matter, but on 64-bit it does).