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

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

# gpg: Signature made Fri May 22 10:00:53 2015 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/block-pull-request: (38 commits)
  block: get_block_status: use "else" when testing the opposite condition
  qemu-iotests: Test unaligned sub-block zero write
  block: Fix NULL deference for unaligned write if qiov is NULL
  Revert "block: Fix unaligned zero write"
  block: align bounce buffers to page
  block: minimal bounce buffer alignment
  block: return EPERM on writes or discards to read-only devices
  configure: Add workaround for ccache and clang
  configure: silence glib unknown attribute __alloc_size__
  configure: factor out supported flag check
  configure: handle clang -nopie argument warning
  block/parallels: improve image writing performance further
  block/parallels: optimize linear image expansion
  block/parallels: add prealloc-mode and prealloc-size open paramemets
  block/parallels: delay writing to BAT till bdrv_co_flush_to_os
  block/parallels: create bat_entry_off helper
  block/parallels: improve image reading performance
  iotests, parallels: check for incorrectly closed image in tests
  block/parallels: implement incorrect close detection
  block/parallels: implement parallels_check method of block driver
  ...

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