priv_data 0/2

Hi,
this is a version of my priv_data patch that updates targets and renames 
functions as suggested by Patrick.

Since xt_init_match() and xt_init_target() (formerly xt_check_match() and 
xt_check_target()) no longer just check and they needed some argument changes 
anyway, I included some more common code previously replicated in 
ip_tables.c, ip6_tables.c and arp_tables.c.
Similarly I introduced xt_destroy_match() and xt_destroy_taget().

The resulting patches are larger than I anticipated, but most of the space is 
taken by function ranames and argument adjustments.

My previous example with xt_condition still applies (just rename checkentry to 
init in struct xt_match).

I tested several combination with iptables, ip6tables and arptables. It can't 
make it fail, but I didn't try it with a real world network load. Right now I 
don't have a 64 bit machine available for testing (I should be able to use 
one in a few days), so I didn't test compat at all.

Testing and comments, as always, are appreciated.

-- 
Saluti,
   Massimiliano Hofer