Trivial patches (2018-12-18)

# gpg: Signature made Tue 18 Dec 2018 14:28:41 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/trivial-patches-pull-request:
  error: Remove NULL checks on error_propagate() calls
  vl: Use error_fatal to simplify obvious fatal errors (again)
  i386: hvf: drop debug printf in decode_sldtgroup
  docs/devel/build-system: fix 'softmu' typo
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>