CppTools: Cancel parsing if editor is closed

The m_parserFuture.cancel() in ~BuiltinEditorDocumentProcessor() did not
cancel anything. Thus, closing a document while the parser was running
led to a blocking UI thread.

Now it cancels at the next include directive it encounters.

Change-Id: I092fddbbd747e0bc95265b6e9b4fcc26b3f76cb3
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/cpptools/baseeditordocumentprocessor.cpp

@@ -77,7 +77,7 @@ void BaseEditorDocumentProcessor::runParser(QFutureInterface<void> &future,
         return;
     }
 
-    parser->update(workingCopy);
+    parser->update(future, workingCopy);
     CppToolsBridge::finishedRefreshingSourceFiles({parser->filePath()});
 
     future.setProgressValue(1);