I was looking into adding a confirmation prompt for '!' and it
isn't very promising due to sequencing issues. (The check for
whether '!' is allowed should happen before the prompt about
running it but the latter should take place in the core rather
than in the port code.) In the mean time, I noticed that VMS was
ignoring the SHELLERS value from SYSCF.
Untested implementation of a SHELLERS check on VMS. Even if it
works, it should not be using $USER as the user name to verify.
Tweaks the Unix implementation of check_user_string() but doesn't
switch the testing loop to the simpler version used by VMS which
is derived from the generic users test used by Qt.
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