slirp updates

# gpg: Signature made Tue 29 Mar 2016 00:16:05 BST using RSA key ID FB6B2F1D
# gpg: Good signature from "Samuel Thibault <samuel.thibault@gnu.org>"
# gpg:                 aka "Samuel Thibault <sthibault@debian.org>"
# gpg:                 aka "Samuel Thibault <samuel.thibault@inria.fr>"
# gpg:                 aka "Samuel Thibault <samuel.thibault@labri.fr>"
# gpg:                 aka "Samuel Thibault <samuel.thibault@ens-lyon.org>"
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: 900C B024 B679 31D4 0F82  304B D017 8C76 7D06 9EE6
#      Subkey fingerprint: F632 74CD C630 0873 CB3D  29D9 E3E5 1CE8 FB6B 2F1D

* remotes/thibault/tags/samuel-thibault:
  Rework ipv6 options
  Use C99 flexible array instead of 1-byte trailing array
  Avoid embedding struct mbuf in other structures
  slirp: send icmp6 errors when UDP send failed
  slirp: Fix memory leak on small incoming ipv4 packet
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>