Workaround to get leader/follower compiling on recent Linuxes:

apr_atomic.h includes some <asm/*.h> header files that clash
with stdlib.h, so I've moved apr_atomic.h so that it's included
after all the other header files.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@94734 13f79535-47bb-0310-9956-ffa450edef68