Initial libmnl porting attempt
Update configure script to link with -lmnl
Fix netlink.c to (almost) build
Fix HAVE_TCA_STATS(2) checks in configure.in
Restructure to compile with all combos of HAVE_TCA_STATS(2)

We want to compile with all combinations of
HAVE_TCA_STATS(2) set/unset and at the same time
protect against submitting the stats twice (if both
are supported).
Introduce "stats_found" and set and attribute on it
to avoid having the compiler complain about it.
This allows us to bury the specific structs under
each HAVE_TCA_STATS(2) #if ...
More fixing of netlink build with different HAVE_...
libmnl: fix 2 mistakes preventing building with --enable-debug
netlink: fix segfault & make advanced options work again

A type mismatch and offset mistake was preventing the interface list
from getting iterated. This was making collectd segfault when the
"QDisc", "Class" or "Filter" options were enabled.
netlink: indentation & whitespace/tab consistency
netlink: comments & cleanup
netlink: __attribute__ usage clarification

As requested by @octo in GitHub#376.
update README to mention libmnl dependency
update build system to reflect switch to libmnl

"./configure" was previously checking for libnetlink and setting
"-lmnl" if found, which was obviously calling for trouble. With
this patch, the last references to libnetlink are dead and buried.

NB: linux/netlink.h and friends are still included here and there
though, but these are not related to libnetlink.
Fix pointer confusion for nested attribute parsing

A reference to a pointer is passed as data,
the resulting attribute payload should be stored in
the dereferenced location to return it to the caller.
use pkg-config to locate libmnl and configure netlink plugin
Add sigrok to README/AUTHORS

Signed-off-by: Florian Forster <octo@collectd.org>
remove redundant inclusion of time.h
update copyright and authors list
Merge remote-tracking branch 'origin/pr/376'
disable fields not available in varnish 2.0.x

Several fields were added in commit 8775392. 3 of them make the build
fail when varnish 2.0.x is used. This patch makes them available only
when using varnish 3.x.

The commit message of 8775392 gives more detail on the rationale behind
this way of doing.