libcdtr is a minilib for Constrained Delaunay TRiangulation using
incremental algorithm, as described in: Yizhi Lu and Wayne Wei-Ming Dai,
"A numerical stable algorithm for constructing constrained Delaunay
triangulation and application to multichip module layout," China.,
1991 International Conference on Circuits and Systems, Shenzhen, 1991,
pp. 644-647 vol.2.

The API is documented in cdt.h. An example is function autotest() in
cdt_test.c.

Limitations:
 - there is a rectangular bounding box initialized with non-removable
   constrained edges on cdt_init(). These boundary constrained edges
   can be split by inserting points.

