function isNegativeZero( x ) {
	return (x === 0.0 && 1.0/x === NINF);
}
Tests if a double-precision floating-point numeric value is negative zero.

@param {number} x - value to test
@returns {boolean} boolean indicating whether the value is negative zero

@example
var bool = isNegativeZero( -0.0 );
// returns true

@example
var bool = isNegativeZero( 0.0 );
// returns false