Function calcPowell

tests/testfn.h:916–920

	&calcPowerSum, NULL };

static double calcPowell( const double* const x, const int N )
{
	return( sqr(x[2]+10.0*x[0])+5.0*sqr(x[1]-x[3])+sqr(sqr(x[0]-2.0*x[1]))+
		10.0*sqr(sqr(x[2]-x[3])) );
}

static const CTestFn TestFnPowell = { "Powell", 4, -4.0, 5.0, 0.0,
	&calcPowell, NULL };