Currently, it isn't legal to perform <, >, <=, or >= rich comparisons on any complex objects, even though these operations are mathematically well-defined for real numbers.

The attached PR addresses this by defining rich comparisons for real-valued complex objects against subclasses of int and float, as well as for decimal.Decimal and fractions.Fraction types. They still raise TypeErrors when either of the operands has a nonzero imaginary part.