Backported from 2.1. Stable for me in various loads.
without the non-portable atomic code available and enabled in APR, this is going to hurt performance, right? (more mutex operations performed in mainline path for the unlucky who use the non-portable atomics???) is it noticeable?
the atomics in the pending apr-1.0-dev still leave much to be desired :( no compare-and-swap interface even on common platforms such as Solaris/Sparc and AIX... though Greg got c-a-s working on PPC yesterday; I'd expect AIX to be supported soon...
