An ACL mask entry. Mask entries are unnamed. During permission checks,
the mask entry interacts with all ACL entries that are members of the group
class. This consists of all named user entries, the unnamed group entry,
and all named group entries. For each such entry, any permissions that are
absent from the mask entry are removed from the effective permissions used
during the permission check.
Returns the enum constant of this type with the specified name.
The string must match exactly an identifier used to declare an
enum constant in this type. (Extraneous whitespace characters are
name - the name of the enum constant to be returned.