screen and slippy map downloading not in sync when below or above 85 degr latitude

[dieterdreist]

screen and slippy map downloading are not in sync when below or above 85 degr latitute:
if you move the editor window close to the poles and then do a "download", having the slippy map tab (in the download window) open will silently clamp you to 85 degrees, regardless of the map projection you have set in the preferences for the map.

I also get a wrong hint about the "download area too large; will probably be rejected by the server" (on the bounding box tab).

Also, the bounding box tab does not let me modify the numbers for min lat, max lat etc. and it requests invalid coordinates (lat -90.7362453), which in turn are rejected by the download API.