Ports the point/vector foundation of geometry/planar: Side and Signum
(three-valued signs), Limits, FloatPoint (approximate), and the exact
IntPoint/IntVector plus projective RationalPoint/RationalVector.
Arithmetic model per type is documented in each module. The key
simplification over the Java source: Python's unbounded int makes the
exact orientation determinants and rational (x,y,z) coordinates trivial,
so side_of is kept exact (upstream uses a double for speed) and no
BigInteger or CRIT_INT overflow promotion is needed. Rational points use
the projective triple with z=0 denoting the point at infinity.
Tests cover collinearity, determinants beyond Java long range, rational
equality/reduction, and integer/rational promotion.
Ryan Malloy
33cb196bc8