Enlarge DUMPED_HEAP_SIZE

* src/w32heap.c (DUMPED_HEAP_SIZE) [_WIN64 || WIDE_EMACS_INT]:
Enlarge to 21MB.  Reported by Richard Copley <rcopley@gmail.com>.

src/w32heap.c

@@ -114,7 +114,7 @@ typedef struct _RTL_HEAP_PARAMETERS {
    to build only the first bootstrap-emacs.exe with the large size,
    and reset that to a lower value afterwards.  */
 #if defined _WIN64 || defined WIDE_EMACS_INT
-# define DUMPED_HEAP_SIZE (20*1024*1024)
+# define DUMPED_HEAP_SIZE (21*1024*1024)
 #else
 # define DUMPED_HEAP_SIZE (12*1024*1024)
 #endif