Remove default-qt-settings file

I am working on a patch that (finally) makes the default-qt-settings file obsolete. This initial template for the gui settings file is no longer needed after all default values are defined as constants or are dynamically determined at first startup or when using a QScintilla lexer for the first time.

I realized that the environment variable OCTAVE_DEFAULT_QT_SETTINGS is tested at startup and if set, its value is taken as the location of the initial settings file. Is this variable used also outside of run-octave or can it be safely removed?

I can’t say for sure that no one else is using it, but that variable was initially added to allow run-octave to set the location of the default qt settings file. So if that file is no longer needed, I think it is OK to remove any code that handles the environment variable.

After the changes in octave: 2a4980872234 (, can we also remove libgui/ Or is that file still necessary for something?

It doesn’t appear to be used anywhere now so I removed it in the following changeset:

Thanks for removing it, John. I just missed it.