* Do not contact RESTbase in texvc rendering mode and
use the well established tex checking that is already build
into texvc.
* Do not use RESTbase in LaTeXML mode.
Background:
In I1982612e8c6a356e3dbdf447724ac82e5968cc77 RESTbased replaced
texvccheck that was a derivate of texvc designed for people
that wanted to use secure MathML rendering using mathoid.
The integration of mathoid to restbase made this feature obsolete.
However, texvccheck was not only used to check the latex input
that was sent to mathoid, but also the string which was sent to texvc.
Since texvc has already build in tex checking this is not
required and does not improve security.
Finally, users updating from old versions of the math extension
(prior to 2014) that do not have textexvccheck installed,
do not need to compile the texvccheck binary after this change.
PS5: Also treats the case where VisualEditor is not installed.
Bug: T121173
Change-Id: I1bd076b09206869b5ed75280d22e1b36bfb8d8ad
