[patch] [build fix] classes that use JMapViewer shoudn't use OsmMercator directly

[glebius]

Hi!

Fixing #7017 requires that all classes using JMapViewer stop trusting OsmMercator as projection solver. Only tilesources, that know that they are using OsmMercator projection, should use OsmMercator. All upper layers should ask the tilesource for (x,y) ?= (lon, lat) calculations.

I already made this change in the JMapViewer itself. Unfortunately, hiding OsmMercator required its API change as well, so right now JOSM isn't buildable.

The attached patch makes JOSM to use tileSource instead of direct use of OsmMercator, and apparently fixes build as well.

[xeen]

In 6793/josm:

[build fix] classes that use JMapViewer shoudn't use OsmMercator directly (fixes #9654, patch by glebius)

[stoecker]

Thanks a lot.