Fix buffer overrun under Windows.

src/os/win32/ngx_files.c

diff --git a/src/os/win32/ngx_files.c b/src/os/win32/ngx_files.c
index 424bd65..25690eb 100644
--- a/src/os/win32/ngx_files.c
+++ b/src/os/win32/ngx_files.c
@@ -228,7 +228,8 @@
     ngx_uint_t          collision;
     ngx_atomic_uint_t   num;
 
-    name = ngx_alloc(to->len + 1 + 10 + 1 + sizeof("DELETE"), log);
+    name = ngx_alloc(to->len + 1 + NGX_ATOMIC_T_LEN + 1 + sizeof("DELETE"),
+                     log);
     if (name == NULL) {
         return NGX_ENOMEM;
     }