Fix for -z option being ignored in openpgp mode and incorrect filenames

[Russtopia]

See https://forums.gentoo.org/viewtopic-t-1070876.html

Summary: default (openpgp) mode does not properly handle addition and stripping of .gz/.bz
file components, resulting in mismatching plaintext/decoded file names and misleads
the user to believe openpgp ciphertext has been first compressed using external tools.

mcrypt w/default config uses openpgp, but does not indicate that the -z option's calls
to external gzip or bzip are not used in this mode.

As compression before encryption is generally considered good for security, this is
misleading and use of -z with the default openpgp mode should cause an error informing
that the openpgp mode will not use external gzip/bzip tools prior to encryption.

In addition, the .gz/.bz path component should not be added if the program is
using openpgp mode and will not call gzip or bzip. Doing so results, on decryption,
with a misleading .gz/.bz extension to the resulting (uncompressed) plaintext.

Steps to Reproduce

1. echo "plaintext" >foo.txt
2. mcrypt -z foo.txt

Result: foo.txt.gz.nc is written. Note this should be foo.txt.nc, as by default openpgp mode is active and no call to gzip is performed.

3. mcrypt -dz foo.txt.gz.nc

Result: foo.txt.gz is written (which is plaintext, not a .gz file), *not* foo.txt

[Russtopia]

Hello? Is anyone there?

Who is current upstream for this project?

[Russtopia]

Bump. If anyone is still here please consider merging. Thanks.