Reported by the new script 'scripts/copyright.pl'. The script has a
regex whitelist for the files that don't need copyright headers.
Removed three (mostly usesless) README files from docs/
Closes#5141
- Clarify that FILE and SCP are disabled by default since 7.19.4
- Add that SMB and SMBS are disabled by default since 7.40.0
- Add CURLPROTO_SMBS to the list of protocols