Hardware-accurate ROM mirroring is now applied to all cartridges smaller
than 4MB. By rounding the ROM size up to the next power-of-two and
mapping it repeatedly across the 4MB window:
1. It matches real hardware mirroring behavior.
2. It prevents FAME/M68K Fetch table misses where Fetch[n] would be 0.
3. It fixes SIGSEGV crashes caused by the CPU jumping to unmapped
memory regions within the cartridge space.
ZengGengSen
733c711a47