claws-plugins-*: Update SRC_URI

* modules are now in one bigger tarball on sourceforge
  http://sourceforge.net/projects/sylpheed-claws/files/extra%20plugins/
* old tarballs are still available in plugins_obsolete directory

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
webkit-efl: Fix build with gcc-4.8