Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20150528' into staging

A set of patches add support for vector registers on s390x.
Notable: Floating point registers and vector registers overlap,
so extra care is needed so that we end up with a consistent state
in all cases.

# gpg: Signature made Thu May 28 09:37:27 2015 BST using RSA key ID C6F02FAF
# gpg: Good signature from "Cornelia Huck <huckc@linux.vnet.ibm.com>"
# gpg:                 aka "Cornelia Huck <cornelia.huck@de.ibm.com>"

* remotes/cohuck/tags/s390x-20150528:
  s390x: Enable vector processing capability
  s390x: Migrate vector registers
  s390x: Add vector registers to ELF dump
  linux/elf.h update
  s390x: Add vector registers to HMP output
  s390x: gdb updates for vector registers
  gdb-xml: Include XML for s390 vector registers
  s390x: Store Additional Status SIGP order
  s390x: Vector Register IOCTLs
  s390x: Common access to floating point registers

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>