Move set_filename() calls outside of parse_file()

Remove the boolean parameter from parse_file; the code is more readable
by having an explicit call to set_filename() where necessary, rather
than a boolean parameter.

Signed-off-by: Alberto Mardegan <mardy@users.sourceforge.net>
Add a Qt main window

This is just an empty window with a File menu and a few items.
It shows how to hook up functions to menu actions.

Signed-off-by: Alberto Mardegan <mardy@users.sourceforge.net>