APR fails to compile on recent version of Rawhide (i.e. Fedora Core 5 development) due to incorrect assumptions about PTHREAD_PRIO_INHERIT. Please see for full explanation: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=178997#c1
See also: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=176911
Workaround (as per RPM spec file from Rawhide) is to: export ac_cv_func_pthread_mutexattr_setrobust_np=no export apr_cv_setrobust_with_prio_inherit=no before running ./configure.
Fixed on the trunk: http://svn.apache.org/viewcvs?rev=380120&view=rev