Designer/CppTools: Fix flaky test_gotoslot_withoutProject

The document was not always updated in time.

Change-Id: Iac89985d39a8784e3cbf63dfd42b1c5150775068
Reviewed-by: Christian Stenger <christian.stenger@digia.com>

src/plugins/cpptools/cpptoolseditorsupport.h

@@ -125,6 +125,9 @@ public:
 
     QSharedPointer<SnapshotUpdater> snapshotUpdater();
 
+    /// Checks whether the document is (re)parsed or about to be (re)parsed.
+    bool isUpdatingDocument();
+
 signals:
     void documentUpdated();
     void diagnosticsChanged();