Refactor audio handler to allow switchable engines (ie: XAudio2, DirectSound)

[djtuBIG-MaliceX]

Original report by James Alan Nguyen (Bitbucket: djtubig-malicex, GitHub: djtubig-malicex).

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Currently using waveOut (inherited from Alexey's source). Need to use implementation as demonstrated by kode54's BASSMIDI driver.

[djtuBIG-MaliceX]

Original comment by James Alan Nguyen (Bitbucket: djtubig-malicex, GitHub: djtubig-malicex).

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For reference: https://github.com/kode54/BASSMIDI-Driver/blob/master/bassmididrv_source/bassmididrv.cpp

[djtuBIG-MaliceX]

Original comment by James Alan Nguyen (Bitbucket: djtubig-malicex, GitHub: djtubig-malicex).

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Now that OPL hardware passthrough is implemented, the waveOut handler does not need to run in this playback mode. Currently, this will run but do nothing as it does not make sense to play both software and hardware at the same time due to latency differences.

[djtuBIG-MaliceX]

Original comment by James Alan Nguyen (Bitbucket: djtubig-malicex, GitHub: djtubig-malicex).

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Class separation has commenced. Annoying part 1: self-referred thread using global object reference symbol instead of passed as argument. Next: MidiSynth singleton needs to be refactored to allow for multiple instances.

[djtuBIG-MaliceX]

Original comment by James Alan Nguyen (Bitbucket: djtubig-malicex, GitHub: djtubig-malicex).

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Lowering priroity. This is not necesary at this stage - last attempts broke the handler.