OK, this is the big one. We still keep using `#include` guards only
where we absolutely need to, but with each header now being valid in
isolation, this can now actually help *minimize* the length of each
translation unit's `#include` list. Turns out that after removing all
the duplicates, we only *actually* need to guard 29 headers across all
5 games.
Part of P0285, funded by [Anonymous] and iruleatgames.
Used for Elis' entrance animation. Including an unused unblitting +
blitting function – apparently, ZUN wrote that one before the sloppy
EGC-accelerated wavy unblitting function that I decompiled way back in
6d2fa9f.
Oh well, the latter one is fine in context, since there are no other
sprites on screen during the animation.
Part of P0108, funded by Yanga.
nmlgc