Crate forward_ref

Macros to simplify extending operator traits over references.

Adapted from the Rust core library internal_macros.rs to remove standard library internal attribute annotations and add usage documentation.

Macros

forward_ref_binop	Extend a binary operator trait impl over refs.
forward_ref_op_assign	Extend an assignment operator trait impl over refs.
forward_ref_unop	Extend a unary operator trait impl over refs.