You are right, there are not many changes, and in fact I copied whole folder so also build files were included, what probably led to big troubles to generate differences.
But those files which were amended / changed, are easy to find by date (last update), because all that work I've done around Xmas, so between 26.12.2020 and 27.12.2020. Some of those changes are marked by "//64bit ... " comment, but unfortunately I forgot to do that in each file I changed. But it is also easy to detect them by searching string "long long" which for 64 bit version replaced simply "long" because of length of addresses, however, is not necessary well done, it should be instead some "long_long" declared as long or long long depending of the desired machine, or x86 or x64. It should be actually corrected in the code.
So it's right, it's so small, but not necessary you are missing something. Actually that was a reason why I included whole folder to make it easier at least to compile with MSVC (the project is created in MSVC 2017), to get it working quickly, as a starting point for other compilers, which I didn't test.
I just can say, since I compiled that version, as an "engine" for my CAD, which is compiled in 32bit with 4.4.4 fork and 64bit with my version of 184.108.40.206, with obviously necessary changes in my code (but this time made better in my code, as long_long rather than long or long long, to use the same source for bot 32bit and 64bit), all is running well, as pure 64bit application (there are also MFC included), with fully functioning Allegro for both vector (primitives) and bitmap operations (I do not use Allegro GUI, I created my own one), however, as I underlined before, I'm using GDI driver, which is the only fast enough for direct drawing, what is necessary in my project, especially XOR mode for drawing vectors.