make M_PI visible to msvc
remove uneeded default args to projection ctor (also fixes msvc linking)
Merge pull request #1722 from mapnik/projection-ctor-fix

Projection ctor fix
also clean up pyc files - helps avoid debian packaging issues
Merge branch 'master' of github.com:mapnik/mapnik
add support for background-image to cairo_renderer and refactor into setup function to match agg/grid renderers - closes #1724
simplify scale_denominator interface
throw if scale_factor == 0 instead of hanging and add rendering tests - closes #1100
Merge branch 'master' into clipper