Merge remote-tracking branch 'remotes/riku/tags/pull-linux-user-20151002' into staging

First set of Linux-user que patches for 2.5

# gpg: Signature made Fri 02 Oct 2015 13:38:00 BST 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-20151002:
  linux-user: assert that target_mprotect cannot fail
  linux-user/signal.c: Use setup_rt_frame() instead of setup_frame() for target openrisc
  linux-user/syscall.c: Add EAGAIN to host_to_target_errno_table for
  linux-user: add name_to_handle_at/open_by_handle_at
  linux-user: Return target error number in do_fork()
  linux-user: fix cmsg conversion in case of multiple headers
  linux-user: remove MAX_ARG_PAGES limit
  linux-user: remove unused image_info members
  linux-user: Treat --foo options the same as -foo
  linux-user: use EXIT_SUCCESS and EXIT_FAILURE
  linux-user: Add proper error messages for bad options
  linux-user: Add -help
  linux-user: Exit 0 when -h is used

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