ES1370 emulation to use it.
TODO #1: implement real sound input in the lowlevel sound modules
TODO #2: implement sound input in the SB16
TODO #3: rewrite sound output code to use the same API
- es1370: fixed transfer size for the ADC channel
- es1370: call startwaveplayback() when the DAC2 channel is activated
- added missing change to BX_SUPPORT_SOUNDLOW
- changed type of variable "stereo" to bx_bool
- minor other changes
an own header file for the basic sound output class. When ready we should
have a separate 'soundmod' plugin that could be used by other soundcard
implementations.