NAME
       ChangeExtSpriteA -- Change the sprite image pointer. (V39)

   SYNOPSIS
       ChangeExtSpriteA( vp, oldsprite, newsprite, tags)
                          a0  a1         a2         a3

        success=ChangeExtSpriteA(struct viewport *, struct extsprite *,
                        struct extsprite *, struct taglist *);

        success=ChangeExtSprite(vp,old_sp,new_sp,tag,....);

   FUNCTION 
        Attempt to change which sprite is displayed for a given
        sprite engine.

   INPUTS
       vp - pointer to viewport structure that this sprite is
                  relative to,  or 0 if relative only top of view
        oldsprite - pointer the old extsprite structure
        newsprite - pointer to the new extsprite structure.

   RESULTS 
        success - 0 if there was an error.
   BUGS 

   SEE ALSO
        freesprite() changesprite() movesprite() allocspritedataa()
        graphics/sprite.h