Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

fixes for 2.9-rc1, plus removal of -mno-cygwin references

# gpg: Signature made Mon 20 Mar 2017 11:25:07 GMT
# gpg:                using RSA key 0xBFFBD25F78C7AE83
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>"
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>"
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* remotes/bonzini/tags/for-upstream:
  hax: fix breakage in locking
  configure: remove Cygwin
  xen: do not build backends for targets that do not support xen
  qemu-ga: obey LISTEN_PID when using systemd socket activation

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