So even TH01 wasn't 100% C++ after all. Turns out that this function
was the only instance in all of REIIDEN.EXE where ReC98 previously had
different encodings for identical x86 instructions.
Part of P0096, funded by Ember2528.
tiles_invalidate_around() must have had the hardest function signature
to figure out in all of PC-98 Touhou… because it seems impossible to
handle all three ways of passing parameters. No way around separately
declaring it in every translation unit then, with the parameter list
expected by that segment's code generation.
Part of P0089, funded by [Anonymous] and Blue Bolt.
Adding op/, main/, and end/ directories does nicely cover a great
majority of the "not really further classifiable slices" implied in
d56bd45.
Part of P0086, funded by [Anonymous] and Blue Bolt.