clipboard-4.1, -4.2, -4.4 fail on macOS

<verbatim>
==== clipboard-4.1 ClipboardLostSel procedure FAILED
==== Contents of test case:

    clipboard append "Test"
    selection clear -s CLIPBOARD
    clipboard get

---- Test completed normally; Return code was: 0
---- Return code should have been one of: 1
==== clipboard-4.1 FAILED


==== clipboard-4.2 ClipboardLostSel procedure FAILED
==== Contents of test case:

    clipboard append "Test"
    clipboard append -t TEST "Test2"
    selection clear -s CLIPBOARD
    clipboard get

---- Test completed normally; Return code was: 0
---- Return code should have been one of: 1
==== clipboard-4.2 FAILED


==== clipboard-4.4 ClipboardLostSel procedure FAILED
==== Contents of test case:

    clipboard append "Test"
    clipboard append -t TEST "Test2"
    clipboard append "Test3"
    selection clear -s CLIPBOARD
    clipboard get

---- Test completed normally; Return code was: 0
---- Return code should have been one of: 1
==== clipboard-4.4 FAILED
</verbatim>