Noise channel matches silicon

The noise implementation on operator 31 matches silicon measurements now.

Keyon fixed

This release fixes the key-on problem that was present on track code 0x46 of arcade Contra. It also has a major re-work of the operator module to make it as similar as possible to JT12 -which means that it is probably now very close to the original YM2151 digital circuit. Other changes have been made in the code and some undocumented bugs have been fixed.

A new random test for the register map is in place. Now registers can be throughfully tested. The main simulator engine is now Verilator.

Surprisingly, the code implemented size has not varied, regardless of the many changes...

Originally released in open cores

v1.0

Starts out with copy of Opencores repository