[Xastir] Minor update and clean up to OSM tile code

[Jerry Dunmire]

Hi,
I have committed a minor clean up to the OSM tile code that fixes the
problem I reported earlier with topOSM tile refresh. In addition, the
names of the topOSM map files (.geo) have been changed so that they
will layer properly without setting specific layer values, and an
obsolete executable (tile_test) has been eliminated.

You should manually delete the
/usr/local/share/xastir/maps/Online/OSM_tiled_topOSM*.geo files. They
still work, but have been superseded slightly different names that
will layer properly.

I am still working on a fix for transparency when *Magick is
configured for 16-bit quantums, and I am looking at improving the tile
draw times.

73,
...jerry
KA6HLD