This PR also uses such self-reference to define negate and add
for Complex numbers in a way that is independent of component types.
Also adds a bigint type and verifies that pocomath will then handle
Gaussian integers "for free".
Ensures that if one function is invalidated, then any that depend on it will be.
Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Reviewed-on: #4
