CppTools: Take "-include" files into account

Fixes: QTCREATORBUG-20602
Change-Id: Ibfc518fc64ed75f93265db800558ec1d2e424bb4
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cpptools/builtineditordocumentparser.h

@@ -69,6 +69,7 @@ private:
 
         ProjectExplorer::HeaderPaths headerPaths;
         QString projectConfigFile;
+        QStringList includedFiles;
         QStringList precompiledHeaders;
 
         CPlusPlus::Snapshot snapshot;