Error importing netgen.gui

Hi Dow,

I could reproduce the issue on Ubuntu 18.04. As can be seen in your link.txt, libXmu is linked BEFORE togl. Since the linking order matters, it's not needed at that time and dropped. After that, togl is linked with dependencies on libXmu (which remain undefined).

It's fixed now on master:
Netgen: 7934a3
NGSolve: c57f7e

Best,
Matthias

Thanks for the fix and for explaining the debugging process so well -- these linker issues are quite complicated!

Best,
Dow