If the macro itself is local to a function, these can work in certain
scenarios, but never for global ones.
Part of P0186, funded by [Anonymous] and Blue Bolt.
The single underscore version is actually slightly more supported among
the compilers I've seen so far. Also added the exact list now.
Part of P0183, funded by Yanga and [Anonymous].
eeb4e7e changed the final C translation unit that used this header to
C++, and we got some more helpful inline functions upcoming.
Part of P0136, funded by [Anonymous].
> assigning to the DI register immediately before a CALL
Yeah, no amount of comma operator trickery can get *that* out of this
compiler. Also, these TH05 .PI functions are the only place in PC-98
Touhou with a `IMUL DI, imm8` instruction, which is impossible to get
out of Turbo C++'s built-in assembler.
Well, at least the `if` branches decompile somewhat nicely.
Part of P0134, funded by [Anonymous].