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/tools/clangbackend/source/clangcodemodelserver.cpp

@@ -258,6 +258,7 @@ static void fillJobRequest(JobRequest &jobRequest, const MessageType &message)
     jobRequest.line = message.line();
     jobRequest.column = message.column();
     jobRequest.ticketNumber = message.ticketNumber();
+    jobRequest.textCodecName = message.fileContainer().textCodecName();
     // The unsaved files might get updater later, so take the current
     // revision for the request.
     jobRequest.documentRevision = message.fileContainer().documentRevision();
@@ -303,6 +304,25 @@ void ClangCodeModelServer::requestFollowSymbol(const RequestFollowSymbolMessage
     }
 }
 
+void ClangCodeModelServer::requestToolTip(const RequestToolTipMessage &message)
+{
+    TIME_SCOPE_DURATION("ClangCodeModelServer::requestToolTip");
+
+    try {
+        const Document document = documents.document(message.fileContainer().filePath(),
+                                                     message.fileContainer().projectPartId());
+        DocumentProcessor processor = documentProcessors().processor(document);
+
+        JobRequest jobRequest = processor.createJobRequest(JobRequest::Type::RequestToolTip);
+        fillJobRequest(jobRequest, message);
+
+        processor.addJob(jobRequest);
+        processor.process();
+    }  catch (const std::exception &exception) {
+        qWarning() << "Error in ClangCodeModelServer::requestToolTip:" << exception.what();
+    }
+}
+
 void ClangCodeModelServer::updateVisibleTranslationUnits(const UpdateVisibleTranslationUnitsMessage &message)
 {
     qCDebug(serverLog) << "########## updateVisibleTranslationUnits";