function round2( x ) {
	return addon( x );
}
Rounds a numeric value to the nearest power of two on a linear scale.

@private
@param {number} x - input value
@returns {number} rounded value

@example
var v = round2( 3.141592653589793 );
// returns 4.0

@example
var v = round2( 13.0 );
// returns 16.0

@example
var v = round2( -0.314 );
// returns -0.25