hello everyone,

this is a proposal to renovate the current libgeometry with a more
modern implementation that i've been using in my personal projects for
the last four years.  it provides almost all of the functionality
available in the old one, with a cleaner and more consistent interface
(similar naming conventions as those used in libdraw's geometric
routines), plus the addition of 2D transformations (not just 3D), a
frame of reference data type for 2- and 3-spaces, and utilities such
as point-in-polygon testing and barycentric coordinate computations.

i documented everything in a single man page—geometry(2)—, so i got
rid of those related to the old library, with the exception of
qball(2), on which i'm still working and whose implementation i
believe to be broken; i'm using a version by BurnZeZ with some minor
changes that actually works, but it doesn't perform rotations the way
it should (demo: https://www.youtube.com/watch?v=g3pha1EXhIk) and i
will need more time to come up with a proper Arcball controller.

some examples of projects where i use the library:

 - http://git.antares-labs.eu/boids/
 - http://git.antares-labs.eu/etoys/
 - http://git.antares-labs.eu/gamephysics/
 - http://git.antares-labs.eu/3dee/


if it looks reasonable to you, i can push it upstream.



cheers!

-rodri