Add item about support for large files on MS-Windows.

etc/TODO

@@ -484,6 +484,13 @@ when the body only calls primitives.
   the definition of `file-attributes' and `directory-files-and-attributes'
   and from the calls.
 
+** Modify the emulation of `stat' for MS-Windows to support large files.
+  The current version uses the stock Windows definition of `struct
+  stat', where the file's size is returned as a 32-bit integer.  That
+  overflows for files larger than 4GB.  To fix, modify `stat' to use
+  64-bit size, and use a declaration of `struct stat' that supports
+  such sizes.
+
 ** Make language-info-alist customizable.  Currently a user can customize
   only the variable `current-language-environment'.