Update MentOs code to the latest development version.

programs/poweroff.c

@@ -0,0 +1,20 @@
+///                MentOS, The Mentoring Operating system project
+/// @file poweroff.c
+/// @brief  
+/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+#include <sys/reboot.h>
+#include <sys/unistd.h>
+#include <stdio.h>
+
+int main(int argc, char** argv)
+{
+    printf("Executing power-off...\n");
+    reboot(
+        LINUX_REBOOT_MAGIC1,
+        LINUX_REBOOT_MAGIC2,
+        LINUX_REBOOT_CMD_POWER_OFF,
+        NULL);
+    return 0;
+}