Mapsforge: avoid additional simplification about vtm

[devemux86]

I reopen this as we have other cases, like artifacts on lakes due to the extra simplification in code.

See commit 13fd8c4 in issue_39 branch for the needed change.
In screenshots, besides the artifacts fix, we have also much more detail in the map.

Before (with additional simplification):

After (without additional simplification):

@hjanetzek why the need for extra simplification besides that already existed in Mapsforge maps?

[stleusc]

I still see artifacts in water just above the road crossing at the bottom of the map. And also one further up (about 1.5 tiles higher).
Are they fixed now too?

[devemux86]

Those artifacts appear also due to OpenGL - completely different than Mapsforge's software rendering.

For example there was need for tessellation in nosea land 'split' polygons (implemented in #37 and #38).

Maybe additional work is needed in more areas. Please open a new issue for that.