This is needed since src/support calls lots of qt code, and some parts of it
(e.g. QFileInfo) require a running event loop. This fixes bug #4917 which is
a symptom of the problem.
The fix is to create a QCoreApplication for tex2lyx, lyxclient and LyX running
without GUI. In the future this could be extended, i.e. to split up the
frontend Application class in a GUI and a console class, and having the
console class use LyXConsoleApp in the same way as Application now uses
GuiApplication. If that is done, one could also think of moving
support/ConsoleApplication to frontend/console/ConsoleApplication.
