Update RAR5 code to report encryption (#2096)

Update RAR5 code to report encryption (#2096)

Currently, the RAR5 code always reports
`ARCHIVE_READ_FORMAT_ENCRYPTION_UNSUPPORTED` for
`archive_read_has_encrypted_entries`, nor does it set any of the
entry-specific properties, even though it has enough information to
properly report this information. Accurate reporting of encryption is
super useful for applications because reporting an error message such as
"the archive is encrypted, but we don't currently support encryption" is
a lot better than a not generally useful `errno` value and a
non-localizable error string with a confusing and unpredictable error
message.

Fixes #1661