Upgraded the "Int64 GUC" patch in order to conform to f3f06b13308e3 updates. Rebased and tested upon the current master (3f9b9621766). The patch is still needed to be up to date as a part of the xid64 solution.
I see Aleksander worked on this patch (with many other hackers) and marked it as rejected. And now Evgeniy, a new developer wants to continue and rebase this patch and also the patches in another 64-xid thread disregarding the fact that the patch is rejected. It's not a crime. It's rejected, true.