net: Use sk_mark for routing lookup in more places

This patch against v2.6.31 adds support for route lookup using sk_mark in some
more places. The benefits from this patch are the following.
First, SO_MARK option now has effect on UDP sockets too.
Second, ip_queue_xmit() and inet_sk_rebuild_header() could fail to do routing
lookup correctly if TCP sockets with SO_MARK were used.

Signed-off-by: Atis Elsts <atis@mikrotik.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

diff --cc net/ipv4/af_inet.c
Simple merge

diff --cc net/ipv4/ip_output.c
Simple merge

diff --cc net/ipv4/udp.c
Simple merge