wall: allow to specify <message> on command line

wall(1) from sysvinit supports

   # wall I love this company!

semantic, This patch add this functionally to the util-linux wall.

Signed-off-by: Karel Zak <kzak@redhat.com>
wall: make banner sysvinit compatible

Signed-off-by: Karel Zak <kzak@redhat.com>