spu: avoid NULL pSpuIrq

CTR sets 0 irq address, and savestates mess up
spu: fix first sample, don't play ahead
libretro: enable dither for peops plugin
misc: merge from pcsxr r86908

Author: edgbla
CdromId fix;
psxbios: merge from pcsxr r90224-r90227

Author: weimingzhi
psxbios: format()
cdriso: merge from pcsxr r90558

Author: edgbla
cdriso: cbn/cbin detection fix;
misc: merge from pcsxr r91261,r91276

Author: edgbla
Small fixes. 11834, 11836 (Lioncash);
psxbios: don't crash on negative length

Contra Legacy of War does memset(..., -1)
Merge https://github.com/notaz/pcsx_rearmed