Merge remote-tracking branch 'remotes/riku/tags/pull-linux-user-20150127' into staging

linux-user updates since last pull request

# gpg: Signature made Tue 27 Jan 2015 20:52:54 GMT using RSA key ID DE3C9BC0
# gpg: Good signature from "Riku Voipio <riku.voipio@iki.fi>"
# gpg:                 aka "Riku Voipio <riku.voipio@linaro.org>"

* remotes/riku/tags/pull-linux-user-20150127:
  linux-user: support target-to-host SCM_CREDENTIALS
  linux-user: Fix broken m68k signal handling on 64 bit hosts
  mips64-linux-user: Fix definition of struct sigaltstack
  linux-user: Fix ioctl cmd type mismatch on 64-bit targets
  linux-user: translate resource also for prlimit64
  linux-user/signal.c: Remove unnecessary wrapper copy_siginfo_to_user
  linux-user/main.c: Mark end_exclusive() as possibly unused
  linux-user/main.c: Call cpu_exec_start/end on all target archs
  linux-user/arm/nwfpe: Delete unused aCC array
  linux-user/alpha: Add define for NR_shmat to enable shmat syscall
  linux-user/signal.c: Remove current_exec_domain_sig()

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