Expose thread_id in info cpus

Based on patch by Glauber Costa:

To allow management applications like libvirt to apply CPU affinities to
the VCPU threads, expose their ID via info cpus. This patch provides the
pre-existing and used interface from qemu-kvm.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

qmp-commands.hx

@@ -1194,6 +1194,7 @@ Return a json-array. Each CPU is represented by a json-object, which contains:
      "nip": PPC (json-int)
      "pc" and "npc": sparc (json-int)
      "PC": mips (json-int)
+- "thread_id": ID of the underlying host thread (json-int)
 
 Example:
 
@@ -1205,12 +1206,14 @@ Example:
             "current":true,
             "halted":false,
             "pc":3227107138
+            "thread_id":3134
          },
          {
             "CPU":1,
             "current":false,
             "halted":true,
             "pc":7108165
+            "thread_id":3135
          }
       ]
    }