Add support for more sound cards

[viti95]

With the Apogee Sound System fully working, it's possible to add support for more sound cards:

• PC Speaker PWM digital audio (Wolf3D uses a simpler idea that may also work well, 1 bit resolution audio at XXX KHz)
• Covox Speech Thing / LPT DAC / Stereo LPT DAC
• AC97 (JUDAS Apocalyptic Softwaremixing Soundsystem)
• Game Blaster
• Tandy 3-voice
• IBM PS/1 Audio card (DAC)
• Sound Blaster Direct Mode (doesn't require DMA, works like Covox, up to 23KHz)
• Windows Sound System
• Roland RAP-10
• OPL2 (Adlib) PCM digital audio