[RFC 0/3] make skb accessors return void pointers

Hi,

After some more fun with spatch, I've come up with these three patches.

I couldn't figure out why spatch didn't convert one skb_put() place,
and there was one inside a macro it didn't find. Otherwise, it's
pretty much just spatch and changing the functions/prototypes.

I've compiled x86 allyesconfig with this and the skb_put_data() and
more skb_put_zero() conversions, but I'm going to wait for the 0-day
kbuild bot to tell me it succeeded on my branch (pushed all of this
to mac80211-next on the skb-access-cleanups branch) before I submit
all five patches properly.

There's, obviously, no way I'd even have attempted this before having
coccinelle :-)

johannes