Fix broken hidden cursor under release builds on macOS

[Tom94]

What the title says. TL;DR: It is important to marshal bool as bool and not as int. Still need to investigate why exactly, but this got rid of all strange and spooky behaviour I was seeing. The other changes in this PR are not necessary for the code to work, but I'm leaving them in to make things more sane.

[Tom94]

I looked around a bit and it turns out the objective-C interface in question used the BOOL type, which is a typedef'd char from C. So, indeed, it was very incorrect to marshal 4-byte int into a function expecting 1-byte BOOL.

See https://developer.apple.com/documentation/appkit/nsbitmapimagerep/1395538-initwithbitmapdataplanes?language=objc