XInitThread & QT standard "app template"


So, when looking where to add the XInitThread call inside GR, for some
places it’s obvious and for some it’s not.

The gnuradio companion template is an obvious place. For WX, the
“class stdapp” is also a pretty obvious choice because a lot of
external app use that template and so will not require changes.

For QT it’s not as easy. AFAICT, all the example python QT
applications just have their own init code that create the
QApplication themselves. And I think that creating the equivalent of
stdapp inside the qtgui python package could probably be useful for
all python app with qt widget to use. And then I could stick my
XinitThread in there.

For C++ app, well I doubt there is any good solution, it’ll be the job
of whatever app that uses a Qt widget needing multi-threaded gui
access to call this itself.