Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-3.1-pull-request...

Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-3.1-pull-request' into staging

- gdb signal handling fix
- add SO_REUSEPORT
- remove dead-code

# gpg: Signature made Mon 12 Nov 2018 20:48:23 GMT
# gpg:                using RSA key F30C38BD3F2FBE3C
# gpg: Good signature from "Laurent Vivier <lvivier@redhat.com>"
# gpg:                 aka "Laurent Vivier <laurent@vivier.eu>"
# gpg:                 aka "Laurent Vivier (Red Hat) <lvivier@redhat.com>"
# Primary key fingerprint: CD2F 75DD C8E3 A4DC 2E4F  5173 F30C 38BD 3F2F BE3C

* remotes/vivier2/tags/linux-user-for-3.1-pull-request:
  linux-user: Add support for SO_REUSEPORT
  linux-user: Clean up nios2 main loop signal handling
  linux-user: Don't call gdb_handlesig() before queue_signal()
  linux-user: Remove dead error-checking code

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