Improve support for non-latin languages in Mapnik text rendering

by Hermann Kraus for OpenStreetMap

Mapnik has dozens of bugs related to rendering right-to-left (RTL) languages, Unicode and text rendering in general: https://github.com/mapnik/mapnik/wiki/InternationalText These bugs are critical in that they pose to hold back the adoption of OSM in various parts of the world and none of the main Mapnik developers have the unicode experience necessary to solve them. So my job would be to rewrite this part of mapnik.