d/control: libxtables11 is also of Multi-Arch: same

So all library packages are Multi-Arch: same, otherwise marking iptables
M-A: foreign is pretty pointless.
Suggested-by: Michael Biebl <biebl@debian.org>
Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>

debian/control

@@ -51,6 +51,7 @@ Description: transitional dummy package
  This is a transitional dummy package. It can safely be removed.
 
 Package: libxtables11
+Multi-Arch: same
 Architecture: linux-any
 Priority: optional
 Section: libs