Revert "Attempt to fix PSG and Direct Sound desynchronisation but horribly fail. Direct Sound is just not present."

This reverts commit b7120b203955839e4790b23288cd61c0f2673c6d.
sound.c: Remove some of the bitwise-and hacks from fixed-point handling.
Add macros to deal with Q15.17 fixed-point numbers.
Remove a forgotten bitwise-and hack.
Preserve one more digit of the number of clock cycles accumulated in a partial output audio sample. This should resynchronise Pokémon Emerald. At least it doesn't sound like an electric guitar operated by a newbie who sets the distortion knob to 11 anymore.