Although this is a public API break, it only affects users that
were compiling against *_LAST values, and can be trivially
worked around without impacting compilation against older
headers, by the user defining VIR_ENUM_SENTINELS before using
libvirt.h.  It is not an ABI break, since enum values do not
appear as .so entry points.  Meanwhile, it prevents users from
using non-stable enum values without explicitly acknowledging
the risk of doing so.

See this list discussion:
https://www.redhat.com/archives/libvir-list/2012-January/msg00804.html

* include/libvirt/libvirt.h.in: Hide all sentinels behind
LIBVIRT_ENUM_SENTINELS, and add missing sentinels.
* src/internal.h (VIR_DEPRECATED): Allow inclusion after
libvirt.h.
(LIBVIRT_ENUM_SENTINELS): Expose sentinels internally.
* daemon/libvirtd.h: Use the sentinels.
* src/remote/remote_protocol.x (includes): Don't expose sentinels.
* python/generator.py (enum): Likewise.
* tests/cputest.c (cpuTestCompResStr): Silence compiler warning.
* tools/virsh.c (vshDomainStateReasonToString)
(vshDomainControlStateToString): Likewise.

VIR_DOMAIN_XML_UPDATE_CPU flag for virDomainGetXMLDesc may be used to
get updated custom mode guest CPU definition in case it depends on host
CPU. This patch implements the same behavior for host-model and
host-passthrough CPU modes.

The mode can be either of "custom" (default), "host-model",
"host-passthrough". The semantics of each mode is described in the
following examples:

- guest CPU is a default model with specified topology:
    <cpu>
      <topology sockets='1' cores='2' threads='1'/>
    </cpu>

- guest CPU matches selected model:
    <cpu mode='custom' match='exact'>
      <model>core2duo</model>
    </cpu>

- guest CPU should be a copy of host CPU as advertised by capabilities
  XML (this is a short cut for manually copying host CPU specification
  from capabilities to domain XML):
    <cpu mode='host-model'/>

  In case a hypervisor does not support the exact host model, libvirt
  automatically falls back to a closest supported CPU model and
  removes/adds features to match host. This behavior can be disabled by
    <cpu mode='host-model'>
      <model fallback='forbid'/>
    </cpu>

- the same as previous returned by virDomainGetXMLDesc with
  VIR_DOMAIN_XML_UPDATE_CPU flag:
    <cpu mode='host-model' match='exact'>
      <model fallback='allow'>Penryn</model>       --+
      <vendor>Intel</vendor>                         |
      <topology sockets='2' cores='4' threads='1'/>  + copied from
      <feature policy='require' name='dca'/>         | capabilities XML
      <feature policy='require' name='xtpr'/>        |
      ...                                          --+
    </cpu>

- guest CPU should be exactly the same as host CPU even in the aspects
  libvirt doesn't model (such domain cannot be migrated unless both
  hosts contain exactly the same CPUs):
    <cpu mode='host-passthrough'/>

- the same as previous returned by virDomainGetXMLDesc with
  VIR_DOMAIN_XML_UPDATE_CPU flag:
    <cpu mode='host-passthrough' match='minimal'>
      <model>Penryn</model>                        --+ copied from caps
      <vendor>Intel</vendor>                         | XML but doesn't
      <topology sockets='2' cores='4' threads='1'/>  | describe all
      <feature policy='require' name='dca'/>         | aspects of the
      <feature policy='require' name='xtpr'/>        | actual guest CPU
      ...                                          --+
    </cpu>

In case a hypervisor doesn't support the exact CPU model requested by a
domain XML, we automatically fallback to a closest CPU model the
hypervisor supports (and make sure we add/remove any additional features
if needed). This patch adds 'fallback' attribute to model element, which
can be used to disable this automatic fallback.

It's not totally obvious that a failure in

    CPU guest data(x86): host/guest (models, pref="qemu64")

test means one needs to fix

    x86-host+guest,models,qemu64-result.xml

where the expected XML is stored. Better to provide a nice hint in
verbose mode for failed tests.

Auto-indent makes life a bit easier; this patch also drops unused
arguments and replaces a misspelled flag name with two entry points
instead, so that callers don't have to worry about how much spacing
is present when embedding cpu elements.

* src/conf/cpu_conf.h (virCPUFormatFlags): Delete.
(virCPUDefFormat): Drop unused argument.
(virCPUDefFormatBuf): Alter signature.
(virCPUDefFormatBufFull): New prototype.
* src/conf/cpu_conf.c (virCPUDefFormatBuf): Split...
(virCPUDefFormatBufFull): ...into new function.
(virCPUDefFormat): Adjust caller.
* src/conf/domain_conf.c (virDomainDefFormatInternal): Likewise.
* src/conf/capabilities.c (virCapabilitiesFormatXML): Likewise.
* src/cpu/cpu.c (cpuBaselineXML): Likewise.
* tests/cputest.c (cpuTestCompareXML): Likewise.

Repetitive patterns should be factored.  The sign of a good
factorization is a change that kills 5x more lines than it adds :)

* src/conf/domain_conf.c (virDomainDeviceDefParse)
(virDomainSnapshotDefParseString): Use new convenience macros.
* src/conf/storage_conf.c (virStoragePoolDefParseSourceString):
Likewise.
* src/cpu/cpu.c (cpuCompareXML, cpuBaselineXML): Likewise.
* src/esx/esx_vi.c (esxVI_Context_Execute): Likewise.
* src/qemu/qemu_migration.c (qemuMigrationCookieXMLParseStr):
Likewise.
* src/security/virt-aa-helper.c (caps_mockup): Likewise.
* src/test/test_driver.c (testOpenFromFile): Likewise.
* tests/cputest.c (cpuTestLoadXML, cpuTestLoadMultiXML):
Likewise.
* tools/virsh.c (cmdFreecell, makeCloneXML, cmdVNCDisplay)
(cmdTTYConsole, cmdDetachInterface, cmdDetachDisk)
(cmdSnapshotCreate, cmdSnapshotCreateAs, cmdSnapshotCurrent)
(cmdSnapshotList, cmdSnapshotParent): Likewise.

We already have virAsprintf, so picking a similar name helps for
seeing a similar purpose.  Furthermore, the prefix V before printf
generally implies 'va_list', even though this variant was '...', and
the old name got in the way of adding a new va_list version.

global rename performed with:

$ git grep -l virBufferVSprintf \
  | xargs -L1 sed -i 's/virBufferVSprintf/virBufferAsprintf/g'

then revert the changes in ChangeLog-old.

Make virtTestLoadFile allocate the buffer to read the file into.

Fix logic error in virtTestLoadFile, stop reading on the first empty line.

Use virFileReadLimFD in virtTestCaptureProgramOutput to avoid manual
buffer handling.

A few of the tests were missing basic sanity checks, while most
of them were doing copy-and-paste initialization (in fact, some
of them pasted the argc > 1 check more than once!).  It's much
nicer to do things in one common place, and minimizes the size of
the next patch that fixes getcwd usage.

* tests/testutils.h (EXIT_AM_HARDFAIL): New define.
(progname, abs_srcdir): Define for all tests.
(VIRT_TEST_MAIN): Change callback signature.
* tests/testutils.c (virtTestMain): Do more common init.
* tests/commandtest.c (mymain): Simplify.
* tests/cputest.c (mymain): Likewise.
* tests/esxutilstest.c (mymain): Likewise.
* tests/eventtest.c (mymain): Likewise.
* tests/hashtest.c (mymain): Likewise.
* tests/networkxml2xmltest.c (mymain): Likewise.
* tests/nodedevxml2xmltest.c (myname): Likewise.
* tests/nodeinfotest.c (mymain): Likewise.
* tests/nwfilterxml2xmltest.c (mymain): Likewise.
* tests/qemuargv2xmltest.c (mymain): Likewise.
* tests/qemuhelptest.c (mymain): Likewise.
* tests/qemuxml2argvtest.c (mymain): Likewise.
* tests/qemuxml2xmltest.c (mymain): Likewise.
* tests/qparamtest.c (mymain): Likewise.
* tests/sexpr2xmltest.c (mymain): Likewise.
* tests/sockettest.c (mymain): Likewise.
* tests/statstest.c (mymain): Likewise.
* tests/storagepoolxml2xmltest.c (mymain): Likewise.
* tests/storagevolxml2xmltest.c (mymain): Likewise.
* tests/virbuftest.c (mymain): Likewise.
* tests/virshtest.c (mymain): Likewise.
* tests/vmx2xmltest.c (mymain): Likewise.
* tests/xencapstest.c (mymain): Likewise.
* tests/xmconfigtest.c (mymain): Likewise.
* tests/xml2sexprtest.c (mymain): Likewise.
* tests/xml2vmxtest.c (mymain): Likewise.