Clang: Provide tooltips

This includes also the query data for the help system (F1) for an
identifier under cursor.

Regressions (libclang changes necessary):
 - Function signatures do not contain default values.
 - Aliases are not resolved for/at:
   - template types
   - qualified name of a type

Fixes/Improvements:
 - Resolve "auto"
 - On a template type, show also the template parameter.
 - For a typedef like
     typedef long long superlong;
   the tooltip was "long long superlong", which was confusing.
   Now, "long long" is shown.

New:
 - Show first or \brief paragraph of a documentation comment.
 - Show size of a class at definition.
 - Show size of a field member in class definition.

Task-number: QTCREATORBUG-11259
Change-Id: Ie1a07930d0e882015d07dc43e35bb81a685cdeb8
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/cpptools/baseeditordocumentprocessor.cpp

@@ -97,6 +97,13 @@ void BaseEditorDocumentProcessor::setParserConfig(
     parser()->setConfiguration(config);
 }
 
+QFuture<ToolTipInfo> BaseEditorDocumentProcessor::toolTipInfo(const QByteArray &/*codecName*/,
+                                                              int /*line*/,
+                                                              int /*column*/)
+{
+    return QFuture<ToolTipInfo>();
+}
+
 void BaseEditorDocumentProcessor::runParser(QFutureInterface<void> &future,
                                             BaseEditorDocumentParser::Ptr parser,
                                             BaseEditorDocumentParser::UpdateParams updateParams)