Make IM compiled on Win32: add pthread_join() impl.

include/my_pthread.h:
  Add pthread_join() for Windows.

include/my_pthread.h

@@ -130,6 +130,9 @@ void pthread_exit(void *a);	 /* was #define pthread_exit(A) ExitThread(A)*/
 #define my_pthread_setprio(A,B)  SetThreadPriority(GetCurrentThread(), (B))
 #define pthread_kill(A,B) pthread_dummy(0)
 
+#define pthread_join(A,B) \
+  ((WaitForSingleObject((A), INFINITE) != WAIT_OBJECT_0) || !CloseHandle(A))
+
 /* Dummy defines for easier code */
 #define pthread_attr_setdetachstate(A,B) pthread_dummy(0)
 #define my_pthread_attr_setprio(A,B) pthread_attr_setprio(A,B)