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

* remotes/riku/linux-user-for-upstream:
  User mode support for Linux ELF files with no section header
  linux-user: Return correct errno for unsupported netlink socket
  linux-user: Don't overrun guest buffer in sched_getaffinity
  linux-user/uname: Return correct uname string for x86_64
  linux-user: fix gcc-4.9 compiler error on __{get,put]}_user
  signal/ppc/do_setcontext remove __get_user return check
  signal/sparc64_set_context: remove __get_user checks
  signal/ppc/{save,restore}_user_regs remove __put/get error checks
  signal/all/setup_frame remove __put_user checks
  signal/all/do_sigreturn - remove __get_user checks
  signal/all/do_sigaltstack remove __get_user value check
  signal/sparc/restore_fpu_state: remove
  signal/all: remove return value from restore_sigcontext
  signal/all: remove return value from setup_sigcontext
  signal/all: remove return value from copy_siginfo_to_user
  signal/x86/setup_frame: __put_user cleanup
  signal/all: remove __get/__put_user return value reading

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