Merge remote-tracking branch 'remotes/jnsnow/tags/bitmaps-pull-request' into staging

bitmaps pull request

# gpg: Signature made Mon 11 Jun 2018 20:33:09 BST
# gpg:                using RSA key 7DEF8106AAFC390E
# gpg: Good signature from "John Snow (John Huston) <jsnow@redhat.com>"
# Primary key fingerprint: FAEB 9711 A12C F475 812F  18F2 88A9 064D 1835 61EB
#      Subkey fingerprint: F9B7 ABDB BCAC DF95 BE76  CBD0 7DEF 8106 AAFC 390E

* remotes/jnsnow/tags/bitmaps-pull-request:
  qapi: add disabled parameter to block-dirty-bitmap-add
  qapi: add x-block-dirty-bitmap-merge
  qmp: transaction support for x-block-dirty-bitmap-enable/disable
  qapi: add x-block-dirty-bitmap-enable/disable
  block/dirty-bitmap: add lock to bdrv_enable/disable_dirty_bitmap
  block: simplify code around releasing bitmaps
  block: remove bdrv_dirty_bitmap_make_anon

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