Release candidate 2.2.0-rc3

[rockowitz]

Branch 2.2.0-rc3 contains release candidate 3 for ddcutil 2.2.0.

Release candidate 2.2.0-rc3 contains minimal functional changes from 2.2.0-rc2. It has, however, undergone significant cleanup, and syslog message handling has been regularized. For details, see file CHANGELOG.md in the source code and web page Notes for Upcoming ddcutil Release 2.2.0 (draft). The latter has a section specifically describing the changes since 2.2.0-rc2.