riched20: Implement ITextSelection::GetText.
riched20: Implement ITextSelection::GetChar.
riched20: Stub for ITextRange interface and implement ITextDocument::Range.
riched20: Implement IText{Selection, Range}::Get{Start, End}.
riched20: Implement ITextRange::GetText.
riched20: Implement ITextRange::GetChar.
riched20: Implement ITextRange::GetDuplicate.
riched20: Implement ITextSelection::GetDuplicate.
riched20: Implement ITextRange::Collapse.
riched20: Implement ITextSelection::Collapse.
riched20: Partially implement ITextRange::Delete.