Mark QCollator as internal.

The class is private in 5.0, we'll publish it in 5.1

Change-Id: Ia7511db0393528aafa8c8059b4eb1657c8cdcc64
Reviewed-by: Casper van Donderen <casper.vandonderen@nokia.com>

src/corelib/tools/qcollator.cpp

@@ -116,6 +116,8 @@ static const char * const collationStrings[collationStringsCount] = {
     \class QCollator
     \brief The QCollator class compares strings according to a localized collation algorithm.
 
+    \internal
+
     \reentrant
     \ingroup i18n
     \ingroup string-processing