function gammasgn( x ) {
	return addon( x );
}
Computes the sign of the gamma function.

@private
@param {number} x - input value
@returns {number} sign of the gamma function

@example
var v = gammasgn( 1.0 );
// returns 1.0

v = gammasgn( -2.5 );
// returns -1.0

v = gammasgn( 0.0 );
// returns 0.0

v = gammasgn( NaN );
// returns NaN