qemu: add architecture-specific CPU info handling

qemu: add architecture-specific CPU info handling

Extract architecture specific data from query-cpus[-fast] if
available. A new function qemuMonitorJSONExtractCPUArchInfo()
can then call architecture-specific extraction handlers.

Initially, there's a handler for s390 cpu info to
set the halted property depending on the s390 cpu state
returned by QEMU. With this it's still possible to report
the halted condition even when using query-cpus-fast.

Signed-off-by: Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>