http://lists.freedesktop.org/archives/libreoffice/2012-April/029940.html
The RTL_USING #define (set by gbuild for anything that's not public
API) allows to use such classes simply by their name, without having
to use the namespace or do explicit using rtl::OUString (which half
of the sources do anyway).
Change-Id: I7edaf12cd278489cdc1d5ff782f0a86361c13c0a
