In libcurl, CURLINFO_CONDITION_UNMET is used to avoid writing to the
output file if the server did not transfered a file based on time
condition. In the same manner, getting a 304 HTTP response back from the
server, for example after passing a custom If-Match-* header, also
fulfill this condition.
Fixes#5181Closes#5183
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
