Now, arithmetic binary operator traits take operands by value,
but non-copyable types such as `BigUint` should not always moved out when
applying operators.
This commit implements these operators not only for bare structs also
these references.
By-value implementations are forwarded to by-reference implementations
for now. In the future, by-value implementations may be replaced with
more efficient implementations (for example, the implementation that
reuses moved buffers.)
mathematcs.
Import numeric traits and functions that were removed from the standard library.
This also implements `AdditiveIterator` and `MultiplicativeIterator` for
`BigUint` and `BigInt`.
closes#28
gifnksm
Aaron Turon