improve error message when c++11 compiler is not available - refs #2376
enable native svg rendering with 'svg-ng' format in render_to_file refs #2229
port travis fixes from #2380 to master
travis: add back libstdc++ upgrade for c++11 support
travis: fix order of ops
add visual test for #983
fix visual tests (removing accidental debug boxes)
expressions - initial function_call framework implementation (TODO)
register fonts in nik2img util
add visual test mimicking a typographic map

 - Helps prepare for #2377 more
 - More details on typographic maps at http://store.axismaps.com
 - See also #2385 and #678
travis: less JOBS in debug mode [skip ci]
add length method
prefer c++ style comments
format
fix text rendering with line placement on corners