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.h

@@ -43,6 +43,8 @@ class RegisterUnsavedFilesForEditorMessage;
 class RequestDocumentAnnotationsMessage;
 class RequestReferencesMessage;
 class RequestFollowSymbolMessage;
+class RequestToolTipMessage;
+class ToolTipMessage;
 class UnregisterProjectPartsForEditorMessage;
 class UnregisterTranslationUnitsForEditorMessage;
 class UnregisterUnsavedFilesForEditorMessage;
@@ -60,6 +62,7 @@ public:
     virtual void documentAnnotationsChanged(const DocumentAnnotationsChangedMessage &message) = 0;
     virtual void references(const ReferencesMessage &message) = 0;
     virtual void followSymbol(const FollowSymbolMessage &message) = 0;
+    virtual void tooltip(const ToolTipMessage &message) = 0;
 };
 
 } // namespace ClangBackEnd