There were two API in driver.c that were silently masking flags
bits prior to calling out to the drivers, and several others
that were explicitly masking flags bits.  This is not
forward-compatible - if we ever have that many flags in the
future, then talking to an old server that masks out the
flags would be indistinguishable from talking to a new server
that can honor the flag.  In general, libvirt.c should forward
_all_ flags on to drivers, and only the drivers should reject
unknown flags.

In the case of virDrvSecretGetValue, the solution is to separate
the internal driver callback function to have two parameters
instead of one, with only one parameter affected by the public
API.  In the case of virDomainGetXMLDesc, it turns out that
no one was ever mixing VIR_DOMAIN_XML_INTERNAL_STATUS with
the dumpxml path in the first place; that internal flag was
only used in saving and restoring state files, which happened
to be in functions internal to a single file, so there is no
mixing of the internal flag with a public flags argument.
Additionally, virDomainMemoryStats passed a flags argument
over RPC, but not to the driver.

* src/driver.h (VIR_DOMAIN_XML_FLAGS_MASK)
(VIR_SECRET_GET_VALUE_FLAGS_MASK): Delete.
(virDrvSecretGetValue): Separate out internal flags.
(virDrvDomainMemoryStats): Provide missing flags argument.
* src/driver.c (verify): Drop unused check.
* src/conf/domain_conf.h (virDomainObjParseFile): Delete
declaration.
(virDomainXMLInternalFlags): Move...
* src/conf/domain_conf.c: ...here.  Delete redundant include.
(virDomainObjParseFile): Make static.
* src/libvirt.c (virDomainGetXMLDesc, virSecretGetValue): Update
clients.
(virDomainMemoryPeek, virInterfaceGetXMLDesc)
(virDomainMemoryStats, virDomainBlockPeek, virNetworkGetXMLDesc)
(virStoragePoolGetXMLDesc, virStorageVolGetXMLDesc)
(virNodeNumOfDevices, virNodeListDevices, virNWFilterGetXMLDesc):
Don't mask unknown flags.
* src/interface/netcf_driver.c (interfaceGetXMLDesc): Reject
unknown flags.
* src/secret/secret_driver.c (secretGetValue): Update clients.
* src/remote/remote_driver.c (remoteSecretGetValue)
(remoteDomainMemoryStats): Likewise.
* src/qemu/qemu_process.c (qemuProcessGetVolumeQcowPassphrase):
Likewise.
* src/qemu/qemu_driver.c (qemudDomainMemoryStats): Likewise.
* daemon/remote.c (remoteDispatchDomainMemoryStats): Likewise.