function ampbm( x, y ) {
	return addon( x, y );
}
Computes the hypotenuse using the alpha max plus beta min algorithm.

@private
@param {number} x - number
@param {number} y - number
@returns {number} hypotenuse

@example
var h = ampbm( -5.0, 12.0 );
// returns ~13.5