Many highDPI releated bugs in GExperts fixed

I have spent several days now to try and fix the remaining bugs in GExperts that are related to highDPI. I think I nailed most of them but unfortunately I can’t be sure because the possible combinations of monitors and their arrangement and settings is so large. So, if you would like to help out, please compile a new DLL from the current sources and test it. As always: Any bugs should be reported on Sourceforge.