Windows 64bit has 4-byte long values which is not suitable for tracking
disk space usage in the incremental sort code. Let's just make all these
fields int64s.

Author: James Coleman
Discussion: https://postgr.es/m/CAApHDvpky%2BUhof8mryPf5i%3D6e6fib2dxHqBrhp0Qhu0NeBhLJw%40mail.gmail.com
Backpatch-through: 13, where the incremental sort code was added