Channel meters flicker on Fast setting

[nyanpasu64]

don't know why it happens, but CSoundChip2's volume API does not have this problem, and replacing emulation cores will fix it over time.

[nyanpasu64]

fixed for 2a03 and fds by #32, not fixed in legacy chips.

[nyanpasu64]

on overclocked modules, the triangle meter level becomes lower than before (because each frame only sees a small vertical range). the expected workaround is to only update the meter every N ticks when overclocked (N is based off of some rounding algorithm applied to fps/60).