Updated to work with macOS 13

[slavenskoj]

Updated code for macOS 13 and above, replacing the deprecated scanCharacters(from:into:) method:

let charset = CharacterSet.alphanumerics.union(.punctuationCharacters).union(.symbols)
if Scanner(string: string).scanCharacters(from: charset) == nil {
    NSLog("control code!")
    if romanBuffer.isEmpty, kanaBuffer.isEmpty { return false }
    var handled = true
    switch keyCode {
    case 0x33:  // delete key
        deleteBackward(client: client)
        return true
    case 0x24:  // enter key
        handled = false
    case 0x31:  // space
        receive(string: " ", client: client)
    case 0x30:  // tab key
        fixTrailingN(client: client)
    default:
        NSLog("Unexpected Input: keyCode(%lX) flags(%lX)", keyCode, flags.rawValue)
        handled = false
    }
    commitComposition(client: client)
    return handled
}

In macOS 10.15 and later, the newer scanCharacters(from:) method returns a String? value directly rather than using an into parameter. The method returns nil if no matching characters are found, which maintains the same logic as the original code.