Add suffix to the target when compiling the OpenSSL variant.
The $(TARGET) target depends now on the 'envs' target.

The 'all' target doesn't need to depend on envs (and not on dirs)
consequently.
Sort entries of .gitignore and removed duplicates.
Ignore SimpleMail-openssl artifacts.
The DESTDIR now includes revision and OpenSSL-ness.
Copy prepared release archive into current directory.
Added VERSION-TAG file to indicate a version tag.

It should be set to SNAPSHOT, if it is no release. If we are in a
release commit, the file should be empty.

Bumped revsion as we've just released something.
Extend the archive name by the version tag.
Ignore simplemail distribution archive files.