add win32 qemu-thread implementation

For now, qemu_cond_timedwait and qemu_mutex_timedlock are left as
POSIX-only functions.  They can be removed later, once the patches
that remove their uses are in.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

qemu-thread-posix.h

@@ -0,0 +1,18 @@
+#ifndef __QEMU_THREAD_POSIX_H
+#define __QEMU_THREAD_POSIX_H 1
+#include "pthread.h"
+
+struct QemuMutex {
+    pthread_mutex_t lock;
+};
+
+struct QemuCond {
+    pthread_cond_t cond;
+};
+
+struct QemuThread {
+    pthread_t thread;
+};
+
+void qemu_thread_signal(QemuThread *thread, int sig);
+#endif