Always compress metafile when Gzip available, even when encrypting.
Although GPG compresses the data it encrypts, pre-compressing the data
carries little or no overhead and ensures that local unencrypted copies of
the metafiles are always compressed, after generation by brackup or following
retrieval from the target. Previously only local copies of metafiles stored
to an unencrypted target would be compressed, which was inconsistent and
meant local unencrypted copies of metafiles could occupy excessive amounts of
disk space.