Merge remote-tracking branch 'remotes/riku/tags/pull-linux-user-20150616' into staging

linux-user patches for 2.4 softfreeze
second spin with ioctl patch refreshed

# gpg: Signature made Tue Jun 16 08:03:14 2015 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-20150616:
  linux-user: ioctl() command type is int
  linux-user: fix the breakpoint inheritance in spawned threads
  linux-user: use __get_user and __put_user in cmsg conversions
  linux-user: Fix length handling in host_to_target_cmsg
  linux-user: Use abi_ulong for TARGET_ELF_PAGESTART
  linux-user: Allocate thunk size dynamically

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