Since it also sets an activation flag, it does much more in context
than checking for a board. This name also highlights why OP.EXE and
FUUIN.EXE ignore the BGM mode specified in the option menu.
Part of P0216, funded by JonathKane.
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].