Error reporting & miscellaneous patches for 2018-09-24

# gpg: Signature made Mon 24 Sep 2018 16:16:50 BST
# gpg:                using RSA key 3870B400EB918653
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>"
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>"
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-error-2018-09-24:
  MAINTAINERS: Fix F: patterns that don't match anything
  Drop "qemu:" prefix from error_report() arguments
  qemu-error: make use of {error, warn}_report_once_cond
  qemu-error: add {error, warn}_report_once_cond
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>