XCB/XVideo: support parent window with ARGB visual (refs #3581)
X11 inherits properties from the parent window by default. XVideo does not (typically) like ARGB visuals. To create plain RGB window on an ARGB window, we need to force the color map, background and border parameters to non-ARGB values. There is one remaining problem to enable ARGB support in Qt4: the Qt4 video widget has a transparent background by default. This is inadequate in fullscreen mode.