bug#61035: [PATCH] cp: improve help regarding ACLs

[Ondrej Valousek]

> My understanding is that ACLs can be seen as extension over permission bits 
> whereas the extended attributes can store pretty 
> much anything.  I am not saying which approach is (more) correct though.

Exactly my point as well. 
Also, it is not correct to say "cp -p now preserves ACL" because it ALWAYS 
preserved Posix ACLs - it was only not obvious from the man page.
Hence my fix there.
The only change we introduced recently is that "cp -p" not only preserves Posix 
ACLs but also NFSv4 ACLs.