This is a fork of the 1.12 stdlib encoding/json.

This fork differs in the following ways:

• Encoder.SetNonNull(true) outputs brackets/braces for empty slices and maps.
• In handling omitempty, Marshal (and Encode) first call a value's IsZero method if present, omitting the element if IsZero returns true, while including the value if false.
• In handling omitempty, structs that don't have an IsZero method will be omitted if they have the zero value.
• Map keys that are both string-kinded as well as an encoding.TextMarshaler will use the MarshalText method when encoding.
• Map keys that are both string-kinded as well as an encoding.TextUnmarshaler will use the UnmarshalText method when decoding.