For 2.5+ remove back-shell from being built. In master, keep the source code for now (Delete for 2.6+) For 2.5 branch, delete the source as well.
To clarify: In master, remove back-shell from the default backends, but still allow it to be explicitly enabled. In RE25, remove back-shell entirely.
For master: • f4e1549e by Quanah Gibson-Mount at 2020-05-14T17:54:53+00:00 ITS#9236 - don't enable shell if --enable-backends is set, but let it be explicitly built
RE25: Commits: • 8224c1bf by Quanah Gibson-Mount at 2020-05-18T19:14:36+00:00 Issue#9236 - Delete back-shell
RE25: Commits: • 8224c1bf by Quanah Gibson-Mount Issue#9236 - Delete back-shell man page