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
The productname from Microsoft is "Schannel", but in infof/failf
reporting we use "schannel". This removes different versions.
Closes#3243
Reviewed-by: Daniel Stenberg <daniel@haxx.se>