[Tilesathome] Added some testing features to lowzoom.pl

[Damian Sulewski]

Hi,
i added some testing to lowzoom.pl.
here is a short description, more in lowzoom.conf.example.

- first of all, if you do not like it do not enable it.

- if "UseOceantilesDat" is set to 1 each downloaded blank z12 tile will
be compared to oceantiles-z12.dat file, now you can:

-- write an error message to "suspicious_tiles.txt" saying e.g. 
	"2280 1296 : downloaded tile is sea, oceantiles says land"

-- choose to use the dowloaded tile or the information from
oceantiles-z12.dat for the next zoom level

I have done it to find the sea tiles on land and the land tiles on sea.
A tile is supposed to be blank sea if it is 103 bytes, land if 179
bytes.
You can now process "suspicious_tiles.txt" and use your tah client to
fix the tiles or do something else with the file.

I would like to add some more testing, so suggestions are welcome.

Greetings,
Damian


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