Eliminate double definitions.
Eliminate unneeded comments.
In common.scad redefine num_defined(), all_defined() and get_radius().
In geometry.scad:
- change name _dist to _dist2line
- simplify _point_above_below_segment() and triangle_area()
- change some arg names for uniformity (path>>poly)
- change point_in_polygon() to accept the Even-odd rule as alternative
- and other minor edits
Update tests_geometry to the new funcionalities.
99e815f077