This has been around since Zeek v4.1, so it was warned about in Zeek 5.0
LTS and we could've removed it with 5.1.
Also removed merge_top_scope() from the zeek::detail namespace, it's
unused now.
Updated the when-aggregates test somehow. I'm not quite sure what had
been tested there :-/
This also installs symlinks from "zeek" and "bro-config" to a wrapper
script that prints a deprecation warning.
The btests pass, but this is still WIP. broctl renaming is still
missing.
#239