s/reg_t/byte_t/ s/wreg_t/word_t/
Lower the volume by default
Remove direct access to _mem structure

Make _read() return a non-reference.
Make sure all writes go through _write().
Fix DEC HL and INC HL and CB ops
Remove direct accessors of _mem
Write our test code to RAM instead of the rom.
Abstract away the memory model.

Add a Memory class that handles access IO.
Give the ability to override memory regions.
Convert audio over to the new system.
Convert video over to the new system.
Convert controller over to the new system.
Use memory maps for the ram.
Add MBC1 implementation.