CVE-2021-25631: denylist of executable filename extensions possible to bypass under windows

In the LibreOffice 7-1 series in versions prior to 7.1.2, and in the 7-0 series in versions prior to 7.0.5, the denylist can be circumvented by manipulating the link so it doesn't match the denylist but results in ShellExecute attempting to launch an executable type.