Merge remote-tracking branch 'kwolf/for-anthony' into staging
* kwolf/for-anthony:
test-coroutine: add performance test for nesting
coroutine: adding configure option for sigaltstack coroutine backend
coroutine: adding configure choose mechanism for coroutine backend
coroutine: adding sigaltstack method (.c source)
qcow2: Reduce number of I/O requests
qcow2: Add qcow2_alloc_clusters_at()
qcow2: Factor out count_cow_clusters
qmp: convert blockdev-snapshot-sync to a wrapper around transactions
add mode field to blockdev-snapshot-sync transaction item
rename blockdev-group-snapshot-sync
qapi: complete implementation of unions
use QSIMPLEQ_FOREACH_SAFE when freeing list elements
Add 'make check-block'
make check: Add qemu-iotests subset
qemu-iotests: Mark some tests as quick
qcow2: Add error messages in qcow2_truncate
block: handle -EBUSY in bdrv_commit_all()
qcow2: Add some tracing
qed: do not evict in-use L2 table cache entries
Group snapshot: Fix format name for backing file