Log Message:
security/ruby-rex-core: update to 0.1.20

0.1.18 (2021-09-29)

* Land #16, Make the synchronization functions public

0.1.19 (2021-11-15)

* Land #17, Add the stopwatch function

0.1.20 (2021-11-16)

* Merge pull request #18 from zeroSteiner/feat/stopwatch/elapsed_seconds
  Refactor into a Stopwatch module