Combine parse_target() and command_jump() implementations

Combine parse_target() and command_jump() implementations

Merge these two functions from xtables, iptables, ip6tables and
arptables. Both functions were basically identical in the first three,
only the last one required a bit more attention.

To eliminate access to 'invflags' in variant-specific location, move the
call to set_option() into callers. This is actually consistent with
parsing of other options in them.

As with command_match(), use xt_params instead of the different
*_globals objects to refer to 'opts' and 'orig_opts'.

It was necessary to rename parse_target() as it otherwise clashes with a
static function of same name in libxt_SET.

In arptables, the maximum allowed target name is a bit larger, so
introduce xtables_globals.target_maxnamelen defining the value. It is
used in the shared xt_parse_target() implementation.

Implementation of command_jump() in arptables diverted from the others
for no obvious reason. The call to parse_target() was done outside of it
and a pointer to cs->arp was passed but not used inside.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>