vl: Error messages need to go to stderr, fix some

We print a few fatal error messages to stdout instead of stderr.
Reproducer:

    $ qemu-system-x86_64 -g 1024x768
    Option g not supported for this target
    $ qemu-system-x86_64 -g 1024x768 >/dev/null

Fix by printing them with error_report().  This also improves the messages.
The above one becomes

    qemu-system-x86_64: -g 1024x768: Option not supported for this target

Reported-by: Tobi {github.com/tobimensch}
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1464683498-28779-1-git-send-email-armbru@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>

0 files changed, 0 insertions, 0 deletions