Make the CentOS builbbot use different versions of APR, APR-Util, httpd and 
serf with versions newer than 1.9 (aka trunk at current).

* tools/dev/buildbot/slaves/svn-x64-centos/svnbuild.sh: Detect the minor of
    the code being built and choose dependencies accordingly.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1572816 13f79535-47bb-0310-9956-ffa450edef68