The translation units were probably a better place back when most of
the codebase was still compiled in C mode, we only had a few C++ TUs,
almost everything needed to be declared as `extern "C"`, and moving
these declarations into the headers would have been really noisy with
all the `#ifdef __cplusplus` / `#endif` required. Nowadays though,
we've greatly reduced that surface area. And given that headers will
include even more headers as part of the upcoming `#include` cleanup,
it makes sense to make the jump now.
Part of P0284, funded by [Anonymous] and Blue Bolt.
… Wait, we *can* decompile functions with both parameters, no stack
frame, and a Pascal calling convention?! Good that I already forgot how
impossible it was to decompile the first function I looked at that fell
into this category!
Part of P0148, funded by [Anonymous].