Changes:
- 64 bit build with MSYS2 / mingw64 on windows using libraries from MSYS2 instead of custom build ones (more convenient)
- fix a potential overflow bug when a function end matches the last instruction
- enable horizontal scrolling in call graph
- two tooltips
- warn when accidentally opening a file
- License changed to GPL
Most important, the exe provided below is 64 bit, whereas all previously released exe files were 32 bit. I do not have the time to compile for 32 bit, but in general, 32-bit should work at least on windows. This is because a) it worked on previous releases and b) MSYS2 also provides 32 bit and it might be sufficient to simply apply the build instruction for mingw32 instead of mingw64.