function y0( x ) {
	return addon( x );
}
Computes the Bessel function of the second kind of order zero.

@private
@param {number} x - input value
@returns {number} evaluated Bessel function

@example
var v = y0( 0.0 );
// returns -Infinity

@example
var v = y0( 1.0 );
// returns ~0.088

@example
var v = y0( -1.0 );
// returns NaN

@example
var v = y0( Infinity );
// returns 0.0

@example
var v = y0( -Infinity );
// returns NaN

@example
var v = y0( NaN );
// returns NaN