* kwolf/for-anthony: (39 commits)
qemu-iotests: add 036 autoclear feature bit test
qemu-iotests: add qcow2.py set-feature-bit command
fdc-test: introduced qtest read_without_media
fdc: fix implied seek while there is no media in drive
qcow2: fix autoclear image header update
xen: Don't peek behind the BlockDriverState abstraction
xen: Don't change -drive if=xen device name during machine init
block: Replace bdrv_get_format() by bdrv_get_format_name()
qemu-img: document qed format on qemu-img man page
qemu-iotests: COW with many AIO requests on the same cluster
qemu-iotests: Some backing file COW tests
qcow2: Fix avail_sectors in cluster allocation code
qcow2: Simplify calculation for COW area at the end
qcow2: always operate caches in writeback mode
ide: support enable/disable write cache
block: always open drivers in writeback mode
block: add bdrv_set_enable_write_cache
block: copy enable_write_cache in bdrv_append
savevm: flush after saving vm state
block: flush in writethrough mode after writes
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