[SKBUFF]: more backports from upstream 2.6 kernel
kernel.org commits
19633e129c65e5bb62b1af545c5479afcdb01fc4 skbuff: skb_mac_header_was_set is always true on >32 bit
603a8bbe62e54108055fca46ecdd611c10c6cd0a skbuff: don't corrupt mac_header on skb expansion
9bcb97cace615a9f57fca0b9d788e7d234d7fc95 skbuff: Copy csum instead of csum_start/csum_offset
be2b6e62357dd7ee56bdcb05e54002afb4830292 net: Fix skb_copy_expand() handling of ->csum_start
00c5a9834b476a138158fb17d576da751727a9f1 net: Fix corruption of skb csum field in pskb_expand_head() of net/core/skbuff.c