* ext/dl/*: remove DL as it is replaced by Fiddle.
  [Feature #5458] Thanks to Jonan Scheffler <jonanscheffler@gmail.com>
  for this patch

* test/dl/*: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48217 b2dd03c8-39d4-4d8f-98ff-823fe69b080e