The regular master.h is big, uncomfortable in C++ mode, and bloated
with all those portability `#define`s that effectively only cover a
small portion of the PC-98-specific code anyway. So, let's gradually
transition to a new smaller header that is more integrated into the
ReC98 codebase, by simply no longer #including `master.h` in new code.
Which also explains its weird place in the root directory. Even though
`libs/master.lib/` contains plenty of game-specific modifications, it
didn't feel right to have anything in this directory refer to types
from `pc98.h`.
Part of P0124, funded by [Anonymous] and Blue Bolt.
nmlgc