Added dependency check for eml so that the schemas and dtds are not
checked out of CVS if they already exist in the lib directory. This is
based on checking for the key schema or dtd file from the 2.0.0beta6,
2.0.0, and 2.0.1 releases, so if you've messed with this directory in
other ways it won't get picked up. But this allows the distribution to
build more cleanly and other builds to be faster.