Update to grub 2.04
    
    This change updates grub to the 2.04 release. The new release changed how
    grub is built, so the bootstrap and bootstrap.conf files have to be added
    to the dist-git. Also, the gitignore file changed so it has to be updated.
    
    Since the patches have been forward ported to 2.04, there's no need for a
    logic to maintain a patch with the delta between the release and the grub
    master branch. So the release-to-master.patch is dropped and no longer is
    updated by the do-rebase script.
    
    Also since gnulib isn't part of the grub repository anymore and cloned by
    the boostrap tool, a gnulib tarball is included as other source file and
    copied before calling the bootstrap tool. That way grub can be built even
    in builders that only have access to the sources lookaside cache.
    
    Resolves: rhbz#1727279
    
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>