I e-mailed the maintainers of the version of mod_authnz_external for the older Apache 2.0 series and one of them, Sven-Haegar Koch, was kind enough to take a look at the code for the version for 2.4 and provided me a patch.  It wasn’t quite in sync with the code I had but there were only about three lines that needed to be changed so I changed them by hand, recompiled, and it worked!

     So phpMyAdmin, which is protected by this code to limit access to Eskimo North customers, because it had unfortunately become a target for hackers, is now available again.