This patch will probably cause merge conflicts to those trying
to do backports.  The end goal is simple - domaincommon.rng
should be the state of domain.rng pre-patch, with a few lines
tweaked in the header, while domain.rng post-patch is now just
a shell that includes domaincommon.rng and sets the <start>.

* docs/schemas/domain.rng: Move guts...
* docs/schemas/domaincommon.rng: ...to new file.
* docs/schemas/domainsnapshot.rng: Allow new xml.
* docs/schemas/Makefile.am (schema_DATA): Distribute new file.
* tests/domainsnapshotxml2xmlout/full_domain.xml: New test.
* libvirt.spec.in (%files client): Ship new file.  Sort lines.
* mingw32-libvirt.spec.in: Likewise.

Audit all changes to the qemu vm->current_snapshot, and make them
update the saved xml file for both the previous and the new
snapshot, so that there is always at most one snapshot with
<active>1</active> in the xml, and that snapshot is used as the
current snapshot even across libvirtd restarts.

This patch does not fix the case of virDomainSnapshotDelete(,CHILDREN)
where one of the children is the current snapshot; that will be later.

* src/conf/domain_conf.h (_virDomainSnapshotDef): Alter member
type and name.
* src/conf/domain_conf.c (virDomainSnapshotDefParseString)
(virDomainSnapshotDefFormat): Update clients.
* docs/schemas/domainsnapshot.rng: Tighten rng.
* src/qemu/qemu_driver.c (qemuDomainSnapshotLoad): Reload current
snapshot.
(qemuDomainSnapshotCreateXML, qemuDomainRevertToSnapshot)
(qemuDomainSnapshotDiscard): Track current snapshot.

Signed-off-by: NChris Lalancette <clalance@redhat.com>