Automatic setting size hints in all choice controls in ShuttleGui...

... excpet in a few places that populate the choice control late and then
do it explicitly

src/prefs/MidiIOPrefs.cpp

@@ -128,7 +128,6 @@ void MidiIOPrefs::PopulateOrExchange( ShuttleGui & S ) {
                              wxT(""),
                              mHostNames,
                              mHostLabels);
-         S.SetSizeHints(mHostNames);
 
          S.AddPrompt(_("Using: PortMidi"));
       }