Merge remote-tracking branch 'remotes/riku/linux-user-for-upstream' into staging

* remotes/riku/linux-user-for-upstream: (22 commits)
  linux-user: check return value of malloc()
  linux-user: writev Partial Writes
  linux-user: Support target-to-host translation of mlockall argument
  linux-user: clock_nanosleep errno Handling on PPC
  linux-user: Minimum Sig Handler Stack Size for PPC64 ELF V2
  linux-user: Move get_ppc64_abi
  linux-user: Detect fault in sched_rr_get_interval
  linux-user: Handle NULL sched_param argument to sched_*
  linux-user: Detect Negative Message Sizes in msgsnd System Call
  linux-user: Conditionally Pass Attribute Pointer to mq_open()
  linux-user: Make ipc syscall's third argument an abi_long
  linux-user: Properly Handle semun Structure In Cross-Endian Situations
  linux-user: Dereference Pointer Argument to ipc/semctl Sys Call
  linux-user: PPC64 semid_ds Doesnt Include _unused1 and _unused2
  linux-user: add setns and unshare
  linux-user: support ioprio_{get, set} syscalls
  linux-user: support timerfd_{create, gettime, settime} syscalls
  linux-user: fix readlink handling with magic exe symlink
  linux-user: Fix conversion of sigevent argument to timer_create
  linux-user: Fix syscall instruction usermode emulation on X86_64
  ...

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