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

src/threads/thread.c

@@ -1,5 +1,6 @@
 #include "threads/thread.h"
 #include <debug.h>
+#include <hash.h>
 #include <stddef.h>
 #include <random.h>
 #include <stdio.h>
@@ -15,6 +16,7 @@
 #include "threads/vaddr.h"
 #ifdef USERPROG
 #include "userprog/process.h"
+#include "userprog/syscall.h"
 #endif
 
 /* Random value for struct thread's `magic' member.
@@ -660,6 +662,7 @@ init_thread (struct thread *t, const char *name, int nice, int priority,
   t->priority = t->base_priority;
 
   t->exit_status = -1;
+  hash_init (&t->open_files, fd_hash, fd_less, NULL);
 
   old_level = intr_disable ();
   list_push_back (&all_list, &t->allelem);