Add an alias to gmake in superenv

I had a luarock explicitly look ONLY for gmake, FFS.

This should be safe.
Luarocks caveats
Add `brew sh` to the manpage
New formula: libwebsockets-1.22

Libwebsockets is the main C library implementation of the latest websockets protocol.

Refs #16221.
Revert "json-c 0.11"

Apparently the shared library has been split into two libraries on 0.11,
which breaks things that are dependent on the old structure (e.g.
postgis).

See #19068.

This reverts commit a37b4561a6f1664888568ad4c0c44e44d38bee18.
Fix man page formatting
Simplify these tests
Check existence rather than rescue exceptions
wip: first pass at fixing validation