I figured this out shortly after posting ... :( What is happening is that something in the latest glibc or kernel headers (not linked into /usr/include, but glibc was built against the 2.6 kernel and probably grabbed some headers then) convinces apr that sctp is supported, even when the lksctp library is not installed.
So I grabbed the latest release from lksctp.sf.net and installed that; then apache compiled w/o further complaint. So apr's configure needs to do a better job of detecting sctp support and turn it off if the necessary defines are not available. -JimC
