function expm1rel( x ) {
	if ( abs( x ) <= EPS ) {
		return 1.0; // L'Hopital's Rule
	}
	if ( x >= OVERFLOW_THRESHOLD ) {
		return PINF; // L'Hopital's Rule
	}
	return expm1( x ) / x;
}
Computes the relative error exponential.

@param {number} x - input value
@returns {number} function value

@example
var v = expm1rel( 0.0 );
// returns 1.0

@example
var v = expm1rel( 1.0 );
// returns ~1.718

@example
var v = expm1rel( -1.0 );
// returns ~0.632

@example
var v = expm1rel( NaN );
// returns NaN