Update math/wxmaxima from 20.01.3 to 20.02.1

• Add another small tutorial.
• Symbols sidebar: correctly remember additional symbols.
• Unicode chars can now be input using the alt+x method.
• Add a unicode sidebard that isn't shown by default as it starts up slowly.
• Many corrections to the display routine.
• Better scroll wheel support.
• Russian translation update.
• Fix a bug causing part of a fraction not to be displayed.
• Several additional bug fixes.

Approved by: gerald (mentor)