Clean up the patches / redo them.

This package has known vulnerabilities, please investigate and fix if possible:
 CVE-2021-45844, CVE-2021-45845

Some mods are installed under "${PREFIX}/Mod/", some under "${PREFIX}/share/Mod/".
Should these be moved? E.g. "${PREFIX}/freecad/Mod/"?

With Coin 4.0.6, fails without setting env vars:
COIN_EGL=1 COIN_GL_NO_CURRENT_CONTEXT_CHECK=1 FreeCAD
See https://github.com/FreeCAD/FreeCAD/issues/22695#issuecomment-4523986222 for
a possible patch to Coin.
