
A ".old" backup suffix for receipts is lame at best, so lets be a bit more formal and use .mpsaved as I'm already using when backing up the conf files.
Also, only update the receipts if they haven't been updated already (that is, if no receipt.bz2.mpsaved file is found).

git-svn-id: dc463f922b716f8a7bf91846309830e794c23801@25924 d073be05-634f-4543-b044-5fe20cf6d1d6

macports/macports-base,danchr/macports-base,macports/macports-base,neverpanic/macports-base,neverpanic/macports-base,danchr/macports-base