improve configure script to remember the previous value of each dependency in build_tools/menuselect-deps, so that (once it has been written) menuselect can use this information to warn the user when a previously met dependency is no longer met

along the way, change tags used in configure script, menuselect-deps and code for various dependencies to be consistently named



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@154151 65c4cc65-6c06-0410-ace0-fbb531ad65f3