add support for more refined ability to set install paths using the standard

options to configure such as --libdir, --sbindir, etc. All of the default paths
are still the same. (issue #7057, jcollie)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@28747 65c4cc65-6c06-0410-ace0-fbb531ad65f3