Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

Bug fixes for the .dmg image file format.

# gpg: Signature made Fri 04 Jan 2019 11:21:18 GMT
# gpg:                using RSA key 9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <[email protected]>"
# gpg:                 aka "Stefan Hajnoczi <[email protected]>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  dmg: don't skip zero chunk
  dmg: use enumeration type instead of hard coding number
  dmg: fix binary search
  dmg: Fixing wrong dmg block type value for block terminator.

Signed-off-by: Peter Maydell <[email protected]>