Merge pull request #19 from mkaravel/develop

[policies][robustness] properly initialize m_approximation in default segment_ratio constructor
[get_turns] Fix turns generation for double collinear spikes.

Add check if a spike Point is realy an IP.
Merge branch 'develop' of github.com:boostorg/geometry into develop
Merge branch 'develop' of https://github.com/boostorg/geometry into feature/setops