[Bug-gnupod] search rename input verification bug

[Ben Roberts]

I am using gnupod 0.99 and when I was changing the rating on a bunch of
files I accidently used the line
 gnupod_search.pl -m /mnt/ipod --id=">2552" --rating="<20" 
--rename="--rating=40"
instead of
 gnupod_search.pl -m /mnt/ipod --id=">2552" --rating="<20" --rename="rating=40"
instead of warning of invalid input, it went ahead and inserted a new
field in the xml of --album at the beginning of each of the entries like
this
  <file --rating="40" addtime="3254026259" artist="Ace of Base" ...
This was easy enough for me to fix with a quick vim edit, but it
might be good to check the input and make sure it is valid so that
others don't have this problem.