ongoing attempt to implement TypeSystemParser.
go back to own tooltip provider.

The thing is, I thought that CSharpBinding uses LanguateItemTooltipProvider
in MonoDevelop.SourceEditor2.dll, but actually the same type in the same
namespace exists in CSharpBinding.dll!!! So it never used the one in
MonoDevelop.SourceEditor2.dll and there is no doubt that it never works
even for CSharpBinding.