function gammaLanczosSum( x ) {
	return addon( x );
}
Calculates the Lanczos sum for the approximation of the gamma function.

@private
@param {number} x - input value
@returns {number} Lanczos sum approximation

@example
var v = gammaLanczosSum( 4.0 );
// returns ~950.366

@example
var v = gammaLanczosSum( -1.5 );
// returns ~1373366.245

@example
var v = gammaLanczosSum( -0.5 );
// returns ~-699841.735

@example
var v = gammaLanczosSum( 0.5 );
// returns ~96074.186

@example
var v = gammaLanczosSum( 0.0 );
// returns Infinity

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