Method as_bool

Source/Utils/dukglue/dukvalue.h:318–322

various (type-safe) getters

	// various (type-safe) getters
	inline bool as_bool() const {
		if (mType != BOOLEAN)
			throw DukException() << "Expected boolean, got " << type_name();
		return mPOD.boolean;
	}

	inline double as_double() const {
		if (mType != NUMBER)