Merge branch 'vm/stack-growth/saleh' into vm/virtual-memory/saleh

# Conflicts:
#	src/userprog/exception.c
#	src/userprog/process.c
#	src/userprog/syscall.c
#	src/vm/frame.c
#	src/vm/page.c
#	src/vm/page.h

src/threads/thread.h

@@ -145,6 +145,8 @@ struct thread
     struct hash open_files;             /* Hash Table of FD -> Struct File. */
 #endif
 
+    void *curr_esp;
+
     /* Owned by thread.c. */
     unsigned magic;                     /* Detects stack overflow. */
   };