gptgen 1.2.1

This is a minor patch release that contains a single bug fix from late last year. As you can probably tell by the commit history, gptgen is not currently under active development by either myself or the original author anymore (although PRs are welcome), so I decided to go ahead and make a new "official" release with this bug fix, and upload a zip file with precompiled Windows binaries for i386 and amd64. (No Linux binaries. You guys typically know what you're doing, and prefer compiling from source anyway, which is so much faster and easier than it is on Windows.) The zip file with precompiled binaries brings us a little more in line with the old SourceForge project, and will hopefully lower the barrier of entry for Windows users.