LatLon2XY: computes the coordinate transformation from lat/lon to map tile coordinates
Description
The function LatLon2XY(lat,lon,zoom) computes the coordinate transformation from lat/lon to map tile coordinates given a zoom level. It returns the tile coordinates as well as the pixel coordinates within the Tile itself. Thanks to Neil Young (see http://groups.google.com/group/Google-Maps-API/browse_thread/thread/d2103ac29e95696f?hl=en) for providing the formulae used.