conf: force 8 byte alignment for virObjectEvent
conf: force 8 byte alignment for virObjectEvent

We need to be able to cast from virObjectEventPtr to one of
its many subclasses. Some of these subclasses have 8 byte
alignment on 32-bit platforms, but virObjectEventPtr only
has 4 byte alignment.

Previously the virObject base class had 8 byte alignment
but this dropped to 4 byte when converted to inherit from
GObject. This introduces cast alignment warnings on 32-bit:

../../src/conf/domain_event.c: In function 'virDomainEventDispatchDefaultFunc':
../../src/conf/domain_event.c:1656:30: error: cast increases required alignment of target type [-Werror=cast-align]
 1656 |             rtcChangeEvent = (virDomainEventRTCChangePtr)event;
      |                              ^
../../src/conf/domain_event.c:1785:34: error: cast increases required alignment of target type [-Werror=cast-align]
 1785 |             balloonChangeEvent = (virDomainEventBalloonChangePtr)event;
      |                                  ^
../../src/conf/domain_event.c:1896:35: error: cast increases required alignment of target type [-Werror=cast-align]
 1896 |             blockThresholdEvent = (virDomainEventBlockThresholdPtr)event;
      |                                   ^
../../src/conf/domain_event.c: In function 'virDomainQemuMonitorEventDispatchFunc':
../../src/conf/domain_event.c:1974:24: error: cast increases required alignment of target type [-Werror=cast-align]
 1974 |     qemuMonitorEvent = (virDomainQemuMonitorEventPtr)event;
      |                        ^
../../src/conf/domain_event.c: In function 'virDomainQemuMonitorEventFilter':
../../src/conf/domain_event.c:2179:20: error: cast increases required alignment of target type [-Werror=cast-align]
 2179 |     monitorEvent = (virDomainQemuMonitorEventPtr) event;
      |                    ^

Forcing 8-byte alignment on virObjectEventPtr removes the
alignment increase during casts to subclasses.

Reviewed-by: Pavel Hrdina <d4772d05997b8abf035041e3b4f4996380ea7e7a@redhat.com>
Signed-off-by: Daniel P. Berrangé <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

olafhering/libvirt,jfehlig/libvirt,crobinso/libvirt,olafhering/libvirt,olafhering/libvirt,jardasgit/libvirt,jfehlig/libvirt,jardasgit/libvirt,nertpinx/libvirt,jfehlig/libvirt,libvirt/libvirt,zippy2/libvirt,jardasgit/libvirt,jardasgit/libvirt,nertpinx/libvirt,jardasgit/libvirt,libvirt/libvirt,jfehlig/libvirt,libvirt/libvirt,zippy2/libvirt,zippy2/libvirt,nertpinx/libvirt,nertpinx/libvirt,zippy2/libvirt,crobinso/libvirt,olafhering/libvirt,nertpinx/libvirt,crobinso/libvirt,crobinso/libvirt,libvirt/libvirt