The document I previously mentioned also said you have to explicitly instruct the ./configure step to compile with threads. I thought, "I'll bet I forgot to do that last time" so I looked in the log. Hm, I'm sure I ran it without any options. So I unpacked the tar.gz file into /tmp and did the ./configure again. It looks like that option is automatic or somehow he knew I had used it a long time back to generate a 2.1.1 library.

Is there some intelligence here or are threads automatically included now if the support is there, e. g. threaded mysql and a thread library?

I'm running on a Centos 4.4 system. Loaded the default mysql from the repository.