iptables: include /usr/share/xtables/pf.os in PN if it's build

* when libnfnetlink is available (provided by
  meta-networking/recipes-filter/libnfnetlink/libnfnetlink_1.0.1.bb
  it's autodetected and utils subdirectory with pf.os is used.
* unfortunately there isn't configure switch to explicitly disable
  libnfnetlink and it's also in different layer so we cannot add it to
  DEPENDS
* it's undeterminitic, but pf.os is the only difference AFAIK, so not
  worth patching configure switch
* fixes:
  iptables-1.4.15: iptables: Files/directories were installed but not
  shipped
    /usr/share/xtables
    /usr/share/xtables/pf.os

(From OE-Core rev: b789152b56ddbd6761989327cae558558401fd46)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/iptables/iptables_1.4.15.bb

@@ -7,7 +7,7 @@ LICENSE = "GPLv2+"
 LIC_FILES_CHKSUM = "file://COPYING;md5=b234ee4d69f5fce4486a80fdaf4a4263\
                     file://iptables/iptables.c;firstline=13;endline=25;md5=f1028f2401da1c120df27594b2be50ef"
 
-PR = "r0"
+PR = "r1"
 
 RRECOMMENDS_${PN} = "kernel-module-x-tables \
                      kernel-module-ip-tables \
@@ -18,7 +18,7 @@ RRECOMMENDS_${PN} = "kernel-module-x-tables \
                      kernel-module-nf-conntrack-ipv4 \
                      kernel-module-nf-nat \
                      kernel-module-ipt-masquerade"
-FILES_${PN} =+ "${libdir}/xtables/"
+FILES_${PN} =+ "${libdir}/xtables/ ${datadir}/xtables"
 FILES_${PN}-dbg =+ "${libdir}/xtables/.debug"
 
 SRC_URI = "http://netfilter.org/projects/iptables/files/iptables-${PV}.tar.bz2 \