poly2d/: Yet another 2D polygon library (WIP)

poly2d/README

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+poly2d - Yet another 2D polygon library
+=======================================
+
+Why do we need another 2D polygon library, if there are already CGAL,
+Boost, Clipper, GPC, ... ?
+
+All the above are either written in a weird language, are under a
+non-Free license, or simply don't provide the feature set we need
+here. poly2d is written in C, doesn't depend on non-standard
+libraries, and is licensed under the GPL (will change to LGPL).
+
+poly2d serves itself liberally from code already in cameo but
+provides a simpler and cleaner interface. The first objective is
+to provide the tools to replace the (badly broken) area filling
+operation in cameo. Later, poly2d could replace more parts of
+cameo.
+
+poly2d puts more emphasis on simplicity than on performance. Some
+functions expect clockwise closed polygons that don't self-intersect.
+The table below shows the capabilities
+
+Open     Counter-clockwise
+|  Concave  Min. vertices
+|  |  Self-intersect
+|  |  |  |  |
+Y  Y  Y  Y  0		p2d_contains_poly(b), p2d_free, p2d_free_all,
+			p2d_is_closed, p2d_copy, p2d_reverse, p2d_vertices,
+			p2d_write_gnuplog, p2d_write_gnuplot_all
+Y  Y  Y  Y  1		p2d_read_gnuplot
+-  Y  Y  Y  0		p2d_simplify
+-  Y  -  Y  3		p2d_is_cw
+-  Y  -  -  3		p2d_contains_point, p2d_contains_poly (a),
+-  Y  -  #  3		p2d_area*, p2d_offset*
+
+# CGAL uses ccw, poly2d uses cw. Need to switch.
+
+Not yet implemented:
+- p2d_simplify (low priority - the offsetting from CGAL already covers
+  the main use case)
+
+Not yet specified:
+- subtraction (do we actually need it ?)
+
+Other:
+- change the license from GPL to LGPL
+- change ccw to cw
+- make sure CGAL is only fed ccw ploygons and cw holes
+- transform CGAL's idea of outer polygons into something we can use
+- use more meaningful offset/overlap model for area fill
+- check for memory leaks
+- try to generate dependencies also for *.cpp
+
+Prerequisite:
+libcgal-dev