We used to have an account "ast" as a token to Andrew S. Tannebaum,
the creator of MINIX. The account was disable by default, with no
possible way to login.
It seems it generates more confusion than it is worth, so this removes it.
The default skeleton user profile is still stored into /etc/ast instead
of the usual /etc/skel.
Change-Id: I71818c0bb9580cdecfa9621f8693586fc48d17cb
957a365668