Plus a test example where an instance is initialized to have only addition,
and then that instance is extended to complex numbers, at which point it
has number and complex addition but not negation or subtraction (at all).
Implements a totally simplistic "poortf" mutable typed function and
a picomath instance generator, as well as the very beginnings of a
number type and one generic function and a default full picomath instance.
Also provides some tests which serve as usage examples.
Glen Whitney