Clang: Tool tips for clang query diagnostics

If you hover a diagnostics in for a clang query you get now a simple tool
tip.

Change-Id: I6352dd3d4b9a33c183e69037eac903469b90eea4
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/clangrefactoring/clangqueryhighlighter.h

@@ -44,6 +44,12 @@ public:
 
     bool hasDiagnostics() const;
 
+    ClangBackEnd::DynamicASTMatcherDiagnosticMessageContainers
+    messagesForLineAndColumn(uint line, uint column) const;
+
+    ClangBackEnd::DynamicASTMatcherDiagnosticContextContainers
+    contextsForLineAndColumn(uint line, uint column) const;
+
 protected:
     void highlightBlock(const QString &text) override;