Add pitch and speed parameters to _SNDPLAYCOPY

[Bhsdfa]

New parameters to _SNDPLAYCOPY, the parameters being optional for pitch and speed, so it doesn't break older existing code.

It would look something like this:
_SNDPLAYCOPY [Sound] [, Volume!] [, x!] [, y!] [, z!] [, Pitch!] [, Speed!]
In use:
_SNDPLAYCOPY MenuSong&, 1, 0, 0, 0, 2, 2

SPEED and PITCH should be a value from -32 to 32, 32 being 32 times faster/higher pitch than the normal.

In addition to that, would be nice to be able to change the PITCH and SPEED while the audio is playing, would be really nice for transitions and effects.
_SNDPITCH and _SNDSPEED should be added for that, it would work just like _SNDVOL but for PITCH and SPEED