texmath-0.12.5: test/writer/tex/munder-05.test

<<< native
[ EIdentifier "_ baseline _"
, ESymbol Rel "="
, EUnder
    False (EIdentifier "_ baseline _") (EPhantom (EIdentifier "fail"))
]
>>> tex
{\_\ baseline\ \_} = \underset{\phantom{fail}}{\_\ baseline\ \_}