Introduce new files (domain_addr.[ch]) to provide
an API for domain device handling that could be
shared across the drivers.

A list of data types were extracted and moved there:

 qemuDomainPCIAddressBus -> virDomainPCIAddressBus
 qemuDomainPCIAddressBusPtr -> virDomainPCIAddressBusPtr
 _qemuDomainPCIAddressSet -> virDomainPCIAddressSet
 qemuDomainPCIAddressSetPtr -> virDomainPCIAddressSetPtr
 qemuDomainPCIConnectFlags -> virDomainPCIConnectFlags

Also, move the related definitions and macros.