TBaseVirtualTree disable single letter incremental search #837

        // The "single letter mode" is used to advance quickly from node to node when pressing the same key several times.
        if toNoSingleLetterIncSearch in TreeOptions.MiscOptions then            // gigo
          SingleLetter := false                                                 // gigo
        else                                                                    // gigo
        if (FocusedColumn > -1) and (coNoSingleLetterIncSearch in Header.Columns[FocusedColumn].Options) then // gigo
          SingleLetter := false                                                 // gigo
        else                                                                    // gigo
        SingleLetter := (Length(FSearchBuffer) = 1) and not PreviousSearch and (FSearchBuffer[1] = NewChar);