Update thread structure to add a hash table of open files and initialise it, w/ E

src/threads/thread.h

@@ -2,6 +2,7 @@
 #define THREADS_THREAD_H
 
 #include <debug.h>
+#include <hash.h>
 #include <list.h>
 #include <stdint.h>
 #include "threads/fixed-point.h"
@@ -116,6 +117,7 @@ struct thread
 #ifdef USERPROG
     /* Owned by userprog/process.c. */
     uint32_t *pagedir;                  /* Page directory. */
+    struct hash open_files;             /* Hash Table of FD -> Struct File */
 #endif
 
     /* Owned by thread.c. */