Support ACL

[likan999]

There are separate issues with ACL support here:

1. If the ACL on the original FS grants certain permission to a user, currently the user won't have the same permission on the binded FS; e.g. a write operation will return EACCESS even if the user has write permission on the original FS (granted by ACL);
2. If the ACL on the original FS grants certain permission to a user U1, and the bindfs maps U1 to another user U2, then we should expect the binded FS's ACL grants the permission to user U2; however, currently getfacl shows the permission under U1.

[mpartel]

Thanks, this seems like a reasonable feature request, but it also seems like a non-trivial effort, so unfortunately I can't promise that it'll get done in any reasonable timeframe. PRs are welcome.

Notes:

• Looks like ACLs pass through bindfs as xattrs like system.posix_acl_access and system.posix_acl_default (mentioned here)
• Apparently there's documentation in an old POSIX draft standard