2A03 pulse volume 1 is silent about fceux

[negativeExponent]

volume adjustments for sound channels needs "adjusting" since it can cause final volume to be zero. in this test case, pulse channel at 1 tick has value fo 1. based on this channel computation:
(pulse vol * modifier) / 256
will turn a pulse volume at '1' with a modifier of 255(max volume in audio settings) will result in 0, turning off that channel.

there is a case where a modifier value of 256 will skip these volume adjustments but that doesnt seem to be accesible through fceux' audio settings.

@zeromus @thor2016

[zeromus]

problem only on QT port (ConsoleSoundConf.cpp, around lines 175..)