font_engine : use FT_New_Library/FT_Done_Library with custom memory management (ref #2209 #2210)
scons: fix path remove to be less aggressive
Merge pull request #2241 from mapnik/freetype-new-lib

 FT_New_Library/FT_Done_Library
Merge branch 'master' of github.com:mapnik/mapnik into render-time-variables
font_engine

+ avoid initialising FT_Library per font registration
+ lock register_fonts
slightly better err message
Merge branch 'master' of github.com:mapnik/mapnik into render-time-variables
fix svg_renderer ctor