Merge branch 'system-calls' into 'userprog-oom'

Add Fixes to Memory Leaks, Memory Access Validation, Synchronised Processes and Refactoring

See merge request lab2425_autumn/pintos_22!38

src/userprog/process.c

@@ -343,6 +343,11 @@ process_exit (void)
   uint32_t *pd;
 
   printf ("%s: exit(%d)\n", cur->name, cur->exit_status);
+
+  /* Clean up all open files */
+  hash_destroy (&cur->open_files, fd_cleanup);
+
+  /* Close the executable file. */
   if (cur->exec_file != NULL)
     {
       lock_acquire (&filesys_lock);