Add ol.geom.flat.lineStringCoordinateAtM
Add ol.geom.LineString#getCoordinateAtM
Add tests for ol.geom.LineString#getCoordinateAtM
Use binary search in ol.geom.flat.lineStringCoordinateAtM
Use ol.geom.LineString#getCoordinateAtM in igc example
Merge pull request #1759 from twpayne/interpolate-m

Interpolate-M