qemu-thread: add API for joinable threads

Split from Jan's original qemu-thread-posix.c patch.  No semantic change,
just introduce the new API that POSIX and Win32 implementations will
conform to.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/cpus.c b/cpus.c
index 7b9f8eb..1ada0f5 100644
--- a/cpus.c
+++ b/cpus.c
@@ -910,7 +910,8 @@
         env->halt_cond = g_malloc0(sizeof(QemuCond));
         qemu_cond_init(env->halt_cond);
         tcg_halt_cond = env->halt_cond;
-        qemu_thread_create(env->thread, qemu_tcg_cpu_thread_fn, env);
+        qemu_thread_create(env->thread, qemu_tcg_cpu_thread_fn, env,
+                           QEMU_THREAD_DETACHED);
         while (env->created == 0) {
             qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
         }
@@ -926,7 +927,8 @@
     env->thread = g_malloc0(sizeof(QemuThread));
     env->halt_cond = g_malloc0(sizeof(QemuCond));
     qemu_cond_init(env->halt_cond);
-    qemu_thread_create(env->thread, qemu_kvm_cpu_thread_fn, env);
+    qemu_thread_create(env->thread, qemu_kvm_cpu_thread_fn, env,
+                       QEMU_THREAD_DETACHED);
     while (env->created == 0) {
         qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
     }