Change keyboard shortcut for xf4lock

[Heiko Adams]

Hi,
by fedora's default the shortcut for xflock4 CTRL+ALT+DEL but I'd suggest
to change that shortcut to SUPER+L because this would be more intuitive to
users which used Windows before. And second CTRL+ALT+DEL is the shortcut
for launching the taskmanager on most systems.

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Regards,

Heiko Adams