function exp2( x ) {
	return addon( x );
}
Evaluates the base `2` exponential function.

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

@example
var v = exp2( 3.0 );
// returns 8.0

@example
var v = exp2( -9.0 );
// returns ~0.002

@example
var v = exp2( 0.0 );
// returns 1.0

@example
var v = exp2( NaN );
// returns NaN