d/libxtables12.symbols: add new symbols

New symbols included in libxtables.
Signed-off-by: Arturo Borrero Gonzalez <arturo@debian.org>

debian/libxtables12.symbols

@@ -20,6 +20,8 @@ libxtables.so.12 libxtables12 #MINVER#
  xtables_find_target@Base 1.6.0+snapshot20161117
  xtables_find_target_revision@Base 1.8.0
  xtables_free_opts@Base 1.6.0+snapshot20161117
+ xtables_getethertypebyname@Base 1.8.1
+ xtables_getethertypebynumber@Base 1.8.1
  xtables_init@Base 1.6.0+snapshot20161117
  xtables_init_all@Base 1.6.0+snapshot20161117
  xtables_insmod@Base 1.6.0+snapshot20161117