fix compile errors with vs in bsp/simulator

bsp/simulator/drivers/sd_sim.c

@@ -1,7 +1,9 @@
 #include <rtthread.h>
 #include <stdio.h>
-//#include <stdlib.h>
-//#include <string.h>
+#ifdef _WIN32
+#include <stdlib.h>
+#include <string.h>
+#endif
 #include <dfs_def.h>
 
 // #define SD_TRACE     rt_kprintf