The whole update routine for graphic 57.

A note for all the offset routines from here to DRAW_AT_L8_D2: +$12 and +$13 of an object record are added to the pixel position CALC_PIXEL_XY works out from the object's U, V and Z, to line the sprite up with the object's position. X is pixels right and Y pixels up, so the usual negative values move the sprite left and down. For a still object that is all its update routine does; others call one to set the offset before they move. They all end at the end of DRAW_AT_L16_D12.