H/V counter

[Clownacy]

I live every day of my life in fear of implementing the H/V counter. Fortunately, there are some good test ROMs for it here: https://sonicresearch.org/community/index.php?threads/clownmdemu-the-greatest-mega-drive-emulator-ever-someday.6571/page-3#post-89616

[Clownacy]

The H/V counters now have approximate implementations, however, they do not pass hardware tests.

[Clownacy]

Approximate H-Counter emulation was added in d3cde78.