ntdll: add a warning about running wine as root (resend)

[Austin English]

Didn't receive any feedback on this one last time. Been seeing this a
bit recently in the forums, so adding a warning. No actual
functionality lost.

[Alexandre Julliard]

Austin English  writes:
> Didn't receive any feedback on this one last time. Been seeing this a
> bit recently in the forums, so adding a warning. No actual
> functionality lost.

We've been through this before. There are legitimate reasons for running
as root, and we don't want to have any sort of warning or message box
getting in the way.