collectd: update to 5.5.0

Update collectd, base of Luci statistics, to 5.5.0.

Patches have been refreshed.
write-graphite plugin is now enabled. (see #1351)

I have compile-tested all plugins with ar71xx,
and real-life tested the following plugins:
Conntrack, Processor (CPU), DNS, Interfaces, Wireless, System Load,
Memory, Ping, Uptime

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

utils/collectd/patches/400-fix-olsrd-get-all.patch

@@ -1,6 +1,6 @@
 --- a/src/olsrd.c
 +++ b/src/olsrd.c
-@@ -653,7 +653,7 @@ static int olsrd_read (void) /* {{{ */
+@@ -658,7 +658,7 @@ static int olsrd_read (void) /* {{{ */
    if (fh == NULL)
      return (-1);