iptables: Fix target TRACE issue

iptables: Fix target TRACE issue

The package kmod-ipt-debug builds the module xt_TRACE, which allows
users to use '-j TRACE' as target in the chain PREROUTING of the table
raw in iptables.

The kernel compilation flag NETFILTER_XT_TARGET_TRACE is also enabled so
that this feature which is implemented deep inside the linux IP stack
(for example in sk_buff) is compiled.

But a strace of iptables -t raw -I PREROUTING -p icmp -j TRACE reveals
that an attempt is made to read /usr/lib/iptables/libxt_TRACE.so, which
fails as this dynamic library is not present on the system.

I created the package iptables-mod-trace which takes care of that, and
target TRACE now works!

https://dev.openwrt.org/ticket/16694
https://dev.openwrt.org/ticket/19661

Signed-off-by: Martin Wetterwald <martin.wetterwald@corp.ovh.com>
[Jo-Philipp Wich: also remove trace extension from builtin extension list
                  and depend on kmod-ipt-raw since its required for rules]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
Tested-by: Enrico Mioso <mrkiko.rs@gmail.com>