R57: Add array heads.
Add MgSegmentCallback and scanSegments().
Add GiContext.setStartArrayHead().
Add bezierPointDistantFromPoint, bezierIntersectionWithLine and cross2LineV.
Add doxygen notes.
Add bezierPointLengthFromStart().
Add 'rotateStepAngle' and 'newShapeFixedsize' options. Change drawTextAt().
Draw angle text in the select command.
R57