function gasum( N, x, stride ) {
	return ndarray( N, x, stride, stride2offset( N, stride ) );
}
Computes the sum of absolute values.

@param {PositiveInteger} N - number of indexed elements
@param {NumericArray} x - input array
@param {PositiveInteger} stride - `x` stride length
@returns {number} sum

@example
var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0 ] );

var s = gasum( x.length, x, 1 );
// returns 15.0