[Maxima] -inf vs. minf, tex(), web interface updates

[Robert Dodier]

> (%i1) load("mactex-utilities")$
> (%i2) texput(signum,"\\sgn")$
> (%i3) tex(signum(x));
> $$\sgn\left(x\right)$$

FWIW texput is in the 5.9.3 build (and probably some earlier releases)
so no need to load mactex-utilities.

Robert