function setWrapToString(wrapper, reference, bitmask) {
      var source = (reference + '');
      return setToString(wrapper, insertWrapDetails(source, updateWrapDetails(getWrapDetails(source), bitmask)));
    }
Sets the `toString` method of `wrapper` to mimic the source of `reference`
with wrapper details in a comment at the top of the source body.

@private
@param {Function} wrapper The function to modify.
@param {Function} reference The reference function.
@param {number} bitmask The bitmask flags. See `createWrap` for more details.
@returns {Function} Returns `wrapper`.