Remove trailing spaces and CVS keywords

I just wanted to work on a patch for #1515372: Caching Results, but soon stumbled over git diff showing dozens of whitespace changes in all files. As per the Drupal coding standards, I configured my editors to automatically remove trailing whitespace upon saving, but it seems there are a lot of trailing spaces in your files.
Could you please remove those to make contributing to your module easier? Attached is a patch, where I also removed the – now unneeded – $Id$ tags and fixed two typos in the very first function documentation comment.
Please review and commit!

(Your code also doesn't meet other parts of the standard, like comment line lengths, but these aren't as detrimental to participation as the whitespace issue. (Also I'm not one to talk there, as I haven't managed to update my modules in that respect, either.))