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/libs/clangsupport/clangcodemodelclientinterface.cpp

@@ -53,6 +53,9 @@ void ClangCodeModelClientInterface::dispatch(const MessageEnvelop &messageEnvelo
         case MessageType::FollowSymbolMessage:
             followSymbol(messageEnvelop.message<FollowSymbolMessage>());
             break;
+        case MessageType::ToolTipMessage:
+            tooltip(messageEnvelop.message<ToolTipMessage>());
+            break;
         default:
             qWarning() << "Unknown ClangCodeModelClientMessage";
     }