Make wxInfoBar in the dialogs sample more readable

As usual, when changing the background colour, we need to change the
foreground as well, otherwise the text risks becoming unreadable with
some default text colour values -- as was the case under GTK+ 3 with its
default theme.

samples/dialogs/dialogs.cpp

@@ -686,6 +686,7 @@ MyFrame::MyFrame(const wxString& title)
 
     // ... changing the colours and/or fonts
     m_infoBarAdvanced->SetOwnBackgroundColour(0xc8ffff);
+    m_infoBarAdvanced->SetForegroundColour(0x123312);
     m_infoBarAdvanced->SetFont(GetFont().Bold().Larger());
 
     // ... and changing the effect (only does anything under MSW currently)