texmath-0.12.5: test/writer/mml/mn3.test

<<< native
[ ENumber "2"
, ESymbol Bin "+"
, EGrouped
    [ ENumber "3" , ESymbol Ord "\8290" , EIdentifier "\8520" ]
]
>>> mml
<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mn>2</mn>
    <mo>+</mo>
    <mrow>
      <mn>3</mn>
      <mi>&#8290;</mi>
      <mi>ⅈ</mi>
    </mrow>
  </mrow>
</math>