domain_conf.h: add autoptr cleanup func to virDomainXMLOptionPtr
domain_conf.h: add autoptr cleanup func to virDomainXMLOptionPtr

This will enable code cleanups on code that still relies on
virObjectUnref() this pointer manually.

Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Signed-off-by: Daniel Henrique Barboza <627b089ad62deae9aaf06ccfa2c9056df28927e0@gmail.com>

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