WIP: Restoration project

Restore work applied since master reset:

The repo clean up reset the repo back to June '19. This MR reapplies the diffs that had been reviewed and merged into master after June '19 prior to the reset.

This requires at least 3 reviewers:

• Reviewer 1: @godfryd
• Reviewer 2: @razvan
• Reviewer 3: @wlodek

This code requires extra thorough checks. Please verify that:

• the code compiles (this code was reviewed previously for correctness, it's ok to have only casual checking in this regards)
• verify that the change contains only the necessary files and nothing extra is added
• that no information that's supposed to remain confidential is present. In particular:
  • no customer's confidential information, such as customer name, credentials, keys, domain names, IP addresses
  • no PII (Personal Identifiable Information), such as names, tax identifiers, SSNs, personal e-mails, phones, addresses etc.
  • no security fixes are present during security disclosure process
  • if the change contains submitter's information, make sure he agreed to put his name in the public (some users may prefer to contribute a patch anonymously, to not reveal publicly the information they're using ISC software)

After your review is done, please confirm this with a sentence similar to this: "I <first, last name> confirm there is no sensitive information present in this change."

Example of such statement: kea!537 (comment 92066)