R0 = reason code
+256 for user sprite area, R2 points to sprite name
+512 for user sprite area, R2 points to sprite
unless otherwise specified:
R1 = sprite control block pointer (or +1 for Wimp sprite pool)
R2 = sprite pointer
other registers as appropriate for reason code
This SWI performs various operations on sprites, including
displaying them onto the screen (or printer). Note that these
calls need ColourTrans if you are using them with 256-colour
sprites. Sprites in the system sprite area are not supported.
