texmath-0.13.1: test/writer/mml/mstyleA2.test

<<< native
[ EStyled
    TextBoldItalic
    [ EGrouped [ ENumber "2" , ESymbol Bin "+" , EIdentifier "x" ] ]
]
>>> mml
<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mn mathvariant="bold-italic">2</mn>
    <mo mathvariant="bold-italic">+</mo>
    <mi mathvariant="bold-italic">𝒙</mi>
  </mrow>
</math>