* poppler-page.cc:
       * poppler-private.h:
       * poppler-qt4.h:
       No need to destroy the Splash output device to change its paper color.
       Add the possibility to set flags that affect the rendering (some
       backends supports only some of them, though).
       Add a Page::label to get the label associated with a page.
       Patches by Pino Toscano <pino@kde.org>.