Added atom/var/pixel_x and pixel_y. The pixel offsets are normally 0,0 and
may range anywhere from -32 to 32. (You can get away with larger offsets, but they are not guaranteed to work when the object's grid location goes off the edge of the screen.) These may be used to displace an object
from its natural position in the display grid. This even applies to overlays
and images, so visual effects associated with an object may now extend beyond
the bounds of the object's own icon. In many cases, shifting the pixel offset
of an object may be much more efficient than accomplishing a similar effect
with icon arithmetic.
Screen objects have their own independent system of pixel offsets, consistent
with the independence between map location and screen location. You specify a
pixel offset using this format: screen_loc = "X:pixel_x,Y:pixel_y".
Pixel offsets are a display feature only. They do not affect any of the
range calculations in the view() algorithms or anything like that.