math/wxmaxima: Update to 20.03.1

• Bug fixes.
• Improve support for pre- and post- super- and subscripts.
• Improve documentation.
• Use default web browser instead of wxWidgets' integrated help browser.
• Support for integrating static and some types of animated gif files.
• Provide possibily to pop out interactively animation frames created with draw().
• Provide an option to configure the maximal amount of saved gnuplot data per plot.
• Avoid using stderr.
• Remove unnecessary info dialog at startup.
• Provide right click suggestions for similar command names.

Approved by: gerald (mentor)