Fix Swift 5.7 warnings.

[robo-fish]

The following warning is emitted for a number of function declarations when compiling with Swift 5.7 (Xcode 14 Beta): "Non-'@objc' instance method in extensions cannot be overridden; use 'public' instead"

Changing the access levels of the functions from open to public resolves the warnings.

[jormungand2006]

Hi @dehesa, Apple has already released up to Xcode 14.2, do you plan to merge this pull request with the latest release?

[inc-ali]

@dehesa please accept this pull request :)