TextEditor: Enable tooltips for textmarks

Adjust bookmark code, add tooltips for clang diagnostics.

Change-Id: I489d499f5431fcb29f27611d4350298acb30baac
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/clangcodemodel/clangtextmark.cpp

@@ -79,10 +79,5 @@ void ClangTextMark::setIcon(ClangBackEnd::DiagnosticSeverity severity)
         TextMark::setIcon(errorIcon);
 }
 
-ClangTextMark::ClangTextMark(ClangTextMark &&other) Q_DECL_NOEXCEPT
-    : TextMark(std::move(other))
-{
-}
-
 } // namespace ClangCodeModel