Merge commit 'v2.5.2' into stable-2.6

* commit 'v2.5.2':
  Fix RST formatting in NEWS file
  Update NEWS and bump version for release 2.5.2
  Fix boot=on flag for CDROMs
  KVM: only pass boot flag once

Conflicts:
        NEWS         (trivial, merged the entries)
        configure.ac (trivial, kept ours)

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Bernardo Dal Seno <bdalseno@google.com>