No map with Mapnik renderer and metaTileSize > 63

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Run Mapnik renderer with metaTileSize = 64 or higher
2. Load the map and zoom to level 13


What is the expected output? What do you see instead?

In zoom level 13 and higher, I see a light blue area only, no map.


What version of the product are you using? On what operating system?

latest from default branch, Linux, Mapnik2


Please provide any additional information below.

Maybe there is a limitation for metaTileSize. Then it should be documented, and 
the metaTileSize spinner in preprocessor-gui should stop at 63, and the 
preprocessor should abort when metaTileSize is too high in the ini file.

Original issue reported on code.google.com by [email protected] on 22 May 2013 at 7:24