Use more widely supported options for the "tr" command line utility in dns_freedns.sh

[master-nevi]

…by removing the use of the character class representation option. Fixes #2536

See #2536 for more info.

[dkerr64]

This should be updated to also remove tabs and spaces as well, and maybe even vertical tabs and form feeds. While things may be working just fine now, the subsequent greps and seds assume that spaces have been removed. FreeDNS does not presently have spaces in places that the code is sensitive to, but if that changed in the future this would fail. Hence if "[:space:]" won't work then I would replace with " \r\n\t\v\f" (note blank space within the string)
David

[dkerr64]

Correction to my previous comment. You DO NEED to explicitly have a space character in the string as there ARE spaces that need to be removed for later greps to work. I recommend reverting this pull request and replacing the tr string with " \r\n\t\v\f" (note blank space within the string)

[Neilpang]

@dkerr64
Sorry, please create a new PR to fix it.

Thanks.