[buffer][performance] add boolean to indicate concave rings:
in non concave rings, no turn calculation is necessary
[buffer] reverse negative rings if necessary (for concave pieces and
one-sided buffers)
Merge branch 'develop' of github.com:boostorg/geometry into develop
[buffer][test] enhance display of pieces
[buffer] fix error in comment
[buffer] small change, use Piece i.o. typename ....
[buffer] major fix: we now create concave helper-pieces differently
In the past there was one with a straight line going from one piece to the next.
Now there are two, going from one piece to the point on the geometry, and the
second going from the point on the geomety to the next piece.
They are now zero-volume.
They fix:
1) crossings of sides with flat-ends (unit-test cases curve, field_sprayer, bend_near_start)
2) joins with limited number of points (unit-test cases concave_b_rough, italy_part, nl_part)
3) joins with large distances
4) many self-intersections on remaining aimes-cases
[buffer][test] added unit test using large country multi_polygons
This one is not enabled by default.
Aimes-test is no enabled by default