vl.c: Improve warnings on use of deprecated options

vl.c: Improve warnings on use of deprecated options

Simplify warnings about deprecated options by rewriting them as
"warning: ignoring deprecated option".

Reword -no-kvm-pit-reinjection deprecation warning.

Suggested-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <1446217682-24421-10-git-send-email-ehabkost@redhat.com>
[Squashed in
Message-Id: <1446217682-24421-11-git-send-email-ehabkost@redhat.com>
and updated commit message]
Signed-off-by: Markus Armbruster <armbru@redhat.com>