Fix for bug https://bugzilla.redhat.com/show_bug.cgi?id=618970

The "prepare" hook is called very early in the VM statup process
before device labeling, so that it can allocate ressources not
managed by libvirt, such as DRBD, or for instance create missing
bridges and vlan interfaces.
* src/util/hooks.c src/util/hooks.h: add definitions for new hooks
  VIR_HOOK_QEMU_OP_PREPARE and VIR_HOOK_QEMU_OP_RELEASE
* src/qemu/qemu_process.c: use them in qemuProcessStart and
  qemuProcessStop()

THREADS.txt states that the contents of vm should not be read or
modified while the vm lock is not held, but that the lock must not
be held while performing a monitor command.  This fixes all the
offenders that I could find.

* src/qemu/qemu_process.c (qemuProcessStartCPUs)
(qemuProcessInitPasswords, qemuProcessStart): Don't modify or
refer to vm state outside lock.
* src/qemu/qemu_driver.c (qemudDomainHotplugVcpus): Likewise.
* src/qemu/qemu_hotplug.c (qemuDomainChangeGraphicsPasswords):
Likewise.

Some qemu monitor event handlers were issuing inadequate warning when
virDomainSaveStatus() failed. They copied the message from I/O error
handler without customizing it to provide better information on why
virDomainSaveStatus() was called.

Also add ATTRIBUTE_NONNULL markers.

* src/qemu/qemu_audit.h: The pattern qemuDomainXXXAudit is
inconsistent; prefer qemuAuditXXX instead.
* src/qemu/qemu_audit.c: Reflect the renames.
* src/qemu/qemu_driver.c: Likewise.
* src/qemu/qemu_hotplug.c: Likewise.
* src/qemu/qemu_migration.c: Likewise.
* src/qemu/qemu_process.c: Likewise.

This was also found while investigating

   https://bugzilla.redhat.com/show_bug.cgi?id=670848

An EOF on a domain's monitor socket results in an event being queued
to handle the EOF. The handler calls qemuProcessHandleMonitorEOF. If
it is a transient domain, this leads to a call to
virDomainRemoveInactive, which removes the domain from the driver's
hashtable and unref's it. Nowhere in this code is the qemu driver lock
acquired.

However, all modifications to the driver's domain hashtable *must* be
done while holding the driver lock, otherwise the hashtable can become
corrupt, and (even more likely) another thread could call a different
hashtable function and acquire a pointer to the domain that is in the
process of being destroyed.

To prevent such a disaster, qemuProcessHandleMonitorEOF must get the
qemu driver lock *before* it gets the DomainObj's lock, and hold it
until it is finished with the DomainObj. This guarantees that nobody
else modifies the hashtable at the same time, and that anyone who had
already gotten the DomainObj from the hashtable prior to this call has
finished with it before we remove/destroy it.

This was found while researching the root cause of:

https://bugzilla.redhat.com/show_bug.cgi?id=670848

virDomainUnref should only be called with the lock held for the
virDomainObj in question. However, when a transient qemu domain gets
EOF on its monitor socket, it queues an event which frees the monitor,
which unref's the virDomainObj without first locking it. If another
thread has already locked the virDomainObj, the modification of the
refcount could potentially be corrupted. In an extreme case, it could
also be potentially unlocked by virDomainObjFree, thus left open to
modification by anyone else who would have otherwise waited for the
lock (not to mention the fact that they would be accessing freed
data!).

The solution is to have qemuMonitorFree lock the domain object right
before unrefing it. Since the caller to qemuMonitorFree doesn't expect
this lock to be held, if the refcount doesn't go all the way to 0,
qemuMonitorFree must unlock it after the unref.

Relax the restriction that the hash table key must be a string
by allowing an arbitrary hash code generator + comparison func
to be provided

* util/hash.c, util/hash.h: Allow any pointer as a key
* internal.h: Include stdbool.h as standard.
* conf/domain_conf.c, conf/domain_conf.c,
  conf/nwfilter_params.c, nwfilter/nwfilter_gentech_driver.c,
  nwfilter/nwfilter_gentech_driver.h, nwfilter/nwfilter_learnipaddr.c,
  qemu/qemu_command.c, qemu/qemu_driver.c,
  qemu/qemu_process.c, uml/uml_driver.c,
  xen/xm_internal.c: s/char */void */ in hash callbacks

This is done for two reasons:
- we are getting very close to 64 flags which is the maximum we can use
  with unsigned long long
- by using LL constants in enum we already violates C99 constraint that
  enum values have to fit into int

The new name complies more with the fact that it contains a set of
qemuCapsFlags.

Three new functions (qemuCapsSet, qemuCapsClear, and qemuCapsGet) were
introduced replacing direct bit operations.

The new names comply more with the fact that they are all members of
enum qemuCapsFlags.

Done mechanically with:
$ git grep -l '\bDEBUG0\? *(' | xargs -L1 sed -i 's/\bDEBUG0\? *(/VIR_&/'

followed by manual deletion of qemudDebug in daemon/libvirtd.c, along
with a single 'make syntax-check' fallout in the same file, and the
actual deletion in src/util/logging.h.

* src/util/logging.h (DEBUG, DEBUG0): Delete.
* daemon/libvirtd.h (qemudDebug): Likewise.
* global: Change remaining clients over to VIR_DEBUG counterpart.

Two-argument free functions are uncommon; match the style elsewhere
by caching the callback at creation.

* src/util/hash.h (virHashCreate, virHashFree): Move deallocator
argument to creation.
* cfg.mk (useless_free_options): Add virHashFree.
* src/util/hash.c (_virHashTable): Track deallocator.
(virHashCreate, virHashFree): Update to new signature.
* src/conf/domain_conf.c (virDomainObjListDeinit)
(virDomainObjListInit, virDomainDiskDefForeachPath)
(virDomainSnapshotObjListDeinit, virDomainSnapshotObjListInit):
Update callers.
* src/conf/nwfilter_params.c (virNWFilterHashTableFree)
(virNWFilterHashTableCreate): Likewise.
* src/conf/nwfilter_conf.c (virNWFilterTriggerVMFilterRebuild):
Likewise.
* src/cpu/cpu_generic.c (genericHashFeatures, genericBaseline):
Likewise.
* src/xen/xm_internal.c (xenXMOpen, xenXMClose): Likewise.
* src/nwfilter/nwfilter_learnipaddr.c (virNWFilterLearnInit)
(virNWFilterLearnShutdown): Likewise.
* src/qemu/qemu_command.c (qemuDomainPCIAddressSetCreate)
(qemuDomainPCIAddressSetFree): Likewise.
* src/qemu/qemu_process.c (qemuProcessWaitForMonitor): Likewise.

virHashFree follows the convention described in HACKING that
XXXFree() functions can be called with a NULL argument.

Now that the virHash handling functions call virReportOOMError by
themselves when needed, users of the virHash API no longer need to
do it by themselves. Since users of the virHash API were not
consistently calling virReportOOMError after memory failures from
the virHash code, this has the added benefit of making OOM
reporting from this code more consistent and reliable.

Move the qemudStartVMDaemon and qemudShutdownVMDaemon
methods into a separate file, renaming them to
qemuProcessStart, qemuProcessStop. All helper methods
called by these are also moved & renamed to match

* src/Makefile.am: Add qemu_process.c/.h
* src/qemu/qemu_command.c: Add qemuDomainAssignPCIAddresses
* src/qemu/qemu_command.h: Add VNC port min/max
* src/qemu/qemu_domain.c, src/qemu/qemu_domain.h: Add
  domain event queue helpers
* src/qemu/qemu_driver.c, src/qemu/qemu_driver.h: Remove
  all QEMU process startup/shutdown functions
* src/qemu/qemu_process.c, src/qemu/qemu_process.h: Add
  all QEMU process startup/shutdown functions