Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-4.1-pull-request...

Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-4.1-pull-request' into staging

Fix multi-threaded go runtime crash

# gpg: Signature made Fri 26 Jul 2019 18:34:00 BST
# gpg:                using RSA key CD2F75DDC8E3A4DC2E4F5173F30C38BD3F2FBE3C
# gpg:                issuer "laurent@vivier.eu"
# gpg: Good signature from "Laurent Vivier <lvivier@redhat.com>" [full]
# gpg:                 aka "Laurent Vivier <laurent@vivier.eu>" [full]
# gpg:                 aka "Laurent Vivier (Red Hat) <lvivier@redhat.com>" [full]
# Primary key fingerprint: CD2F 75DD C8E3 A4DC 2E4F  5173 F30C 38BD 3F2F BE3C

* remotes/vivier2/tags/linux-user-for-4.1-pull-request:
  linux-user: Make sigaltstack stacks per-thread

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