function mgf( t, a, b ) {
	return addon( t, a, b );
}
Evaluates the moment-generating function (MGF) of a discrete uniform distribution with minimum support `a` and maximum support `b` at a value `t`.

@private
@param {number} t - input value
@param {integer} a - minimum support
@param {integer} b - maximum support
@returns {number} evaluated MGF

@example
var y = mgf( 2.0, 0, 4 );
// returns ~689.475

@example
var y = mgf( -0.2, 0, 4 );
// returns ~0.697

@example
var y = mgf( 2.0, 0, 1 );
// returns ~4.195

@example
var y = mgf( 0.5, 3, 3 );
// returns ~4.482

@example
var y = mgf( 0.5, 3, 2 );
// returns NaN

@example
var y = mgf( NaN, 0, 1 );
// returns NaN