function log1p( x ) {
	return addon( x );
}
Evaluates the natural logarithm of \\(1+x\\).

@private
@param {number} x - input value
@returns {number} the natural logarithm of `1+x`

@example
var v = log1p( 4.0 );
// returns ~1.609

@example
var v = log1p( -1.0 );
// returns -Infinity

@example
var v = log1p( 0.0 );
// returns 0.0

@example
var v = log1p( -0.0 );
// returns -0.0

@example
var v = log1p( -2.0 );
// returns NaN

@example
var v = log1p( NaN );
// returns NaN