Use QUuid::toByteArray() instead of QUuid::toString().toAscii()

This is a cheaper way.

Change-Id: Ibfc67e0ac46a77e95b2ef32cd6f28c7409c42d63
Reviewed-on: http://codereview.qt.nokia.com/2037
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Liang Qi <liang.qi@nokia.com>

src/gui/text/qrawfont_ft.cpp

@@ -88,7 +88,7 @@ public:
         FaceId faceId;
         faceId.filename = "";
         faceId.index = 0;
-        faceId.uuid = QUuid::createUuid().toString().toAscii();
+        faceId.uuid = QUuid::createUuid().toByteArray();
 
         return init(faceId, true, Format_None, fontData);
     }