*  Write real error messages
*  Support Unicode symbols (probably requires help from the font side, urgh)
*  Don't use TEX_LAYOUT_SPACING for everything, just make it the default
*  Add a parameter to resolve as inline style or display style
*  Support character-level spacing
*  Be more generic in what nodes have display mode by default

*  Add square roots, and honor TEX_SQRT_SLANTED and TEX_SQRT_BAR_LENGTH
*  Add vectors
*  Add limits
*  Add matrices