[underover] Fix display mode for base node and accent computation.
[underover] Fix display mode for base node and accent computation.

wavewave/lasem,janmarthedal/mathml2svg,janmarthedal/mathml2svg,janmarthedal/mathml2svg,gjtorikian/lasem,gjtorikian/lasem,gjtorikian/lasem,wavewave/lasem,wavewave/lasem,janmarthedal/mathml2svg,wavewave/lasem,gjtorikian/lasem