The classic GNU Go gets rebuilt, and in 64-bit too 
While I know about this version of GNU Go 3.8, I decided to build one with a much newer version of the GCC compiler. The new version should be faster (many more optimizations) and is smaller. As I have not found a 64-bit version, I've compiled that one as well. Both are fully functional and working in Drago and GoGui.
Chess engines that use 64-bit bitboards get significantly faster and can thus see further ahead when compiled in 64-bit, and can also use more memory. Pachi becomes a bit slower in 64-bit actually, but it can still use a lot more memory. I don't know if 64-bit has any advantage for GNU Go, but hey... it works, right?
You can download the engine here:
http://asmoda.net/files/gnu_go_3_8_win32_win64.zip
Add the program to GoGui or Drago in the usual way, and append these parameters at the end of the line:
--mode gtp --level 10 --japanese-rules --cache-size 512
"--mode gtp": Necessary.
"--level": from 1 to 10. (I think it goes higher, unofficially.)
"--japanese-rules / --chinese-rules": Japanese or Chinese counting.
"--cache-size": number of megabytes of memory GNU Go can use. 8MB is default. While the 64-bit version can theoretically use gigabytes of RAM, I don't know if GNU Go actually does. (Pachi and Fuego do.)
All options can be found here.
Have fun