gdal2tiles: update epsg 900913 to 3857
|Reported by:||hamish||Owned by:||warmerdam|
epsg 900913 (spherical pseudo merc) is non-standard and so not as robust as ideally it could be (e.g. see #5617).
the attached patch replaces it in swig/.../gdal2tiles.py with epsg:3857, the latest incarnation of an official code for this since epsg:3785 was retired and 41001 is even more non-standard.
I left 900913 in the code comments since most people working with it will know it on sight.