* Update Go to 1.21.
* Update minimum Go version to 1.19.
* Fixup deprecated `io/ioutil`.
* Move errcheck excludes inline.
Signed-off-by: SuperQ <superq@gmail.com>
* Update Makefile.common from prometheus/prometheus.
* Switch from Cirrus to CircleCI.
* Add CHANGELOG.md and VERSION.
* Drop inline /vendor.
* Update references to old github URL.
* Update copyrights.
* Update Go version.
* Skip building on aix (undefined: syscall.Mkfifo)
Signed-off-by: SuperQ <superq@gmail.com>