function kernelLog1p( f ) {
	return addon( f );
}
Computes `log(1+f) - f` for `1+f` in `~[sqrt(2)/2, sqrt(2)]`.

@private
@param {number} f - input value
@returns {number} function value

@example
var v = kernelLog1p( 1.0 );
// returns ~0.1931

@example
var v = kernelLog1p( 1.4142135623730951 );
// returns ~0.4672

@example
var v = kernelLog1p( NaN );
// returns NaN