provide an alternate getloadavg implementation and a fallback for systems that...

provide an alternate getloadavg implementation and a fallback for systems that don't have it at all (issue #5549 with minor mods)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6903 65c4cc65-6c06-0410-ace0-fbb531ad65f3