Add Irem mapper 78

[pinobatch]

Two Irem discrete boards classified as Mapper 78 are used in Uchuusen Cosmo Carrier and Holy Diver. The NES 2.0 submapper selects switchable 1-screen mirroring or switchable H/V mirroring. The test78 ROMs in little things produce "Unsupported iNES mapper: 78".