Update collectd to 5.5.3

Release notes at https://github.com/collectd/collectd/releases/tag/collectd-5.5.3

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

* Bump collectd version to 5.5.2.
* Refresh patches.

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

Update collectd, the backbone of Luci statistics, to 5.5.1

Refresh patches. Main changes:
 - Remove 500-upstream-parallel-build-fix.patch (implemented upstream)
 - Add 600-fix-libmodbus-detection.patch to revert an upstream change
   that broke libmodbus detection in collectd's configure script

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