C++ semantic highlighting: Report uses sorted by line.

This moves sorting from the gui thread to the future and
allows the incremental application of the extra formats
to assume chunks are sorted.

Change-Id: I38e179e573c43cc955cce820f17ac87e3300a839
Reviewed-on: http://codereview.qt.nokia.com/3869
Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>

src/plugins/cppeditor/cppchecksymbols.h

@@ -168,6 +168,7 @@ private:
     QSet<QByteArray> _potentialStatics;
     QList<AST *> _astStack;
     QVector<Use> _usages;
+    unsigned _lineOfLastUsage;
     bool _flushRequested;
     unsigned _flushLine;
 };