function ln( x ) {
	return addon( x );
}
Evaluates the natural logarithm of a double-precision floating-point number.

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

@example
var v = ln( 4.0 );
// returns ~1.386

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

@example
var v = ln( Infinity );
// returns Infinity

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

@example
var v = ln( -4.0 );
// returns NaN