Numerous 64bit uint, int, vs size_t, sizediff_t issues

[apriori]

As happens with many D2 projects, this one also suffers from the usual 64bit issues.

[jacob-carlborg]

The SWT repositories are 32bit. Eclipse have separate code bases for 32 and 64bit platforms. But we might be able to merge these in D. We have some advantage, compared to Java, that makes it quite easy to support both 32 and 64bit in the same code base. On the other hand I don't know much about the Win32 and GTK+ APIs, how much a 32bit application differs from a 64bit application.