Linear mixer option

[Yave-Yu]

Non-linear square channel mixing is a bit distorted, especially two 50% or 75% duty mixing, sounds quite unpleasure, so this option is made for who hates non-linear square channel mixing.

[Yave-Yu]

Also added not reset square phase option (I wish to create another PR, but what the heck it automaticlly added here, seems I need to create another branch), to mimic Dendy and late Famiclone which didn't swap duty cycles.

[negativeExponent]

i think im missing something. "wlinear1" remains at the same value and no effect on high quality sound mode

[Yave-Yu]

I only tested Win32 version, so not sure other version works well…
On Win32 version, it works fine, Low/High/Highest are all work as expect.

LinearMixer.mp4

This video you could hear effect.

As wlinear1, that just take the center value of nonlinear square table, then used to mix with each square channel. This just like NSFPlay's implementation.

[Yave-Yu]

i think im missing something. "wlinear1" remains at the same value and no effect on high quality sound mode

I know the reason… It's because new option just add to Win32 version… Other version need add new option too. Win32 version's Sound now looks like this: