PDF: emit the Trapped entry in the document info dictionary

Since we don't have any API to specify trapping info, mark
the document as untrapped. (PDF/X-4 requires the entry, and
requires it to be true or false. The default would be "unknown"
but that's not allowed by X-4.)

This work has been kindly sponsored by the QGIS project
(https://qgis.org/).

Change-Id: Id8c3a4356ba5bb74877473549e55ccbb6839b07e
Reviewed-by: Albert Astals Cid <aacid@kde.org>

src/gui/painting/qpdf.cpp

@@ -1741,6 +1741,7 @@ void QPdfEnginePrivate::writeInfo()
         xprintf("+%02d'%02d')\n", hours , mins);
     else
         xprintf("Z)\n");
+    xprintf("/Trapped /False\n");
     xprintf(">>\n"
             "endobj\n");
 }