Convert Extruder object (mostly) to C++ with lots of fields.
Make C++ gcode generator use C++ Extruder object directly.
Add XS Extruder files to manifest.
Correctly convert extruder_offset to Point object before passing to C++ code.
Replace multitude of Extruder fields with querying a PrintConfig object by id.
Add REGISTER_CLASS call for Extruder class.
Keep pointer to PrintConfig instead of copying it.
Constify ConfigOptionVector::get_at.
Replace Extruder::config accessor with Perl wrapper, with C++ option accessors.
Add xsp wrapper for Pointf class.
Use -O1 with GCC 4.7.0-4.7.2. #1965
New get_trapezoids() implementation. Maybe heavier but it doesn't fail with some versions of GCC like the one provided by Boost.Polygon. #1965
Test triangulate2() instead of the faulty triangulate()
Merge pull request #1968 from sapir/extrudercpp

Translate Extruder class to C++
Some minor changes to the newly-ported Extruder class
Improvements to bridge angle detection: use coverage test for all cases (including two-sided bridges and C-shaped bridges) and check for all angles equal to directions of bridge sides
Fixed regression causing bad loading of multi-extruder values in GUI. #1984
Bugfix: gap fill was not inserted in the correct order before leaving island. Includes regression test. #1907
Fixed regression and ambiguity about multiple-value placeholders like [first_layer_temperature_1]. Includes several unit tests covering regression. #1899
One more change to multi-value placeholders: indices start from 0. #1899