function deg2radf( x ) {
	return addon( x );
}
Converts an angle from degrees to radians (single-precision).

@private
@param {number} x - angle in degrees
@returns {number} angle in radians

@example
var r = deg2radf( 90.0 );
// returns ~1.571

@example
var r = deg2radf( -45.0 );
// returns ~-0.785

@example
var r = deg2radf( NaN );
// returns NaN