Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-3.0-pull-request...

Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-3.0-pull-request' into staging

Fix safe_syscall() on ppc64 host
Fix mmap() 0 length error case

# gpg: Signature made Tue 31 Jul 2018 09:41:07 BST
# 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-3.0-pull-request:
  linux-user: ppc64: don't use volatile register during safe_syscall
  tests: add check_invalid_maps to test-mmap
  linux-user/mmap.c: handle invalid len maps correctly

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