configure: Fixed check for libsigrok and AM_PATH_GLIB_2_0.
curl_json: also allow long callback names.

This is basically the same as 2f392819, which got applied to the
curl_xml plugin a few months ago.

Fixes #582.
Merge pull request #592 from mfournier/bug-582

curl_json: also allow long callback names.
Merge pull request #630 from llnw/F-METRICS-383-tsdb-writer-5.4

write_tsdb plugin
Revert "write_tsdb plugin"
Merge pull request #677 from collectd/revert-630-F-METRICS-383-tsdb-writer-5.4

Revert "write_tsdb plugin"
Merge pull request #540 from tokkee/configure

configure: Fixed check for libsigrok and AM_PATH_GLIB_2_0.
[METRICS-383] Add Brett Hawn and Kevin Bowling to AUTHORS
[METRICS-383] Default to counters, not rates. Remove unused config code.
[METRICS-383] Add documentation for write_tsdb
Revert "Revert "write_tsdb plugin""

This reverts commit 7771a19a0bee247b8e1da848ab47671bd884c5b9.
Merge branch 'collectd-5.4' into F-METRICS-383-tsdb-writer-5.4
Merge branch 'F-METRICS-383-tsdb-writer-5.4' into LLNW-collectd-5.4