tests: add --debug-text option to lsm-test.
tests: add --debug-text option to lsm-test.

With this option, lasem will show text extents as a thin red rectangle.

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