MFH: r433137

Update to the most recent commit on GitHub which fixes many bugs:

Bugfixes:

• gbsplay:
  • cpu emulation fixes:
    • RLCA/RLA/RRCA/RRA did not set ZF
    • fix botched SBC zero flag handling
    • fix slight bug in ADC/SBC
    • fix INC/DEC SP, CP A and half-carry flag in DEC
    • fix PUSH/POP AF
  • fix trigger handling on noise channel
  • fix error on midi plugout where a write to the file could occur before the file was opened
  • fix garbled screen on exit in verbose mode (gbsplay -v)
  • fix status display: respect channel in left/right total volume
  • fix impulse generator: generate a header file at compile-time

Enhancements:

• gbsplay:
  • more accurate sound:
    • calculate LFSR correctly
    • play first nibble on DAC-channel from fresh buffer
    • correct noise channel speed
    • use more DMG-like DC-offsets
    • more accurate cpu cycle accounting
    • remove DC offset from DAC-channel
  • show register contents in verbose mode (gbsplay -v)
  • add basic GBR file support
  • support ugetab int vector extension (gbs spec 1.04u)
  • add 'iodumper' plugout for testing
  • add support for blargg-gb-tests debug output

Approved by: ports-secteam blanket