package/pseudo: provide better legacy handling for fakeroot

We now have a wrapper that makes pseudo behaves like the fakeroot of the
good ol' days. So the symlink will just magically keep old scripts
working as they did before the switch to pseudo.

However, using fakeroot is deprecated, and we want people to stop using
it altogether and switch to pseudo.

So, make the wrapper recognise how it's called, and if called as
fakeroot, print a warning message.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Gaël PORTAY <gael.portay@savoirfairelinux.com>
Cc: Patrick Keroulas <patrick.keroulas@savoirfairelinux.com>
Cc: Erico Nunes <nunes.erico@gmail.com>
Cc: Julien BOIBESSOT <julien.boibessot@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>