Merge branch 'hotfix/1.21.6' into stable
correction 'warnings' -> 'warning'
Merge pull request #2020 from panth0r/master

minor correction "this warnings" to "this warning"
Removed double listed libc6-dev package from requirements.
Merge pull request #2021 from vakuum/pr-1

Removed double listed libc6-dev package from requirements.
1.21.7
Merge branch 'master' into hotfix/1.21.7
Merge branch 'hotfix/1.21.7'
Merge branch 'master' of github.com:wayneeseguin/rvm