win: ensure 32-bit printf precision

This commit removes a printf warning by casting a 64-bit
value to 32 bits.

Fixes: https://github.com/libuv/libuv/issues/955
PR-URL: https://github.com/libuv/libuv/pull/963
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/win/fs-event.c

@@ -425,7 +425,7 @@ void uv_process_fs_event_req(uv_loop_t* loop, uv_req_t* req,
               }
 
               _snwprintf(filenamew, size, L"%s\\%.*s", handle->dirw,
-                file_info->FileNameLength / sizeof(WCHAR),
+                file_info->FileNameLength / (DWORD)sizeof(WCHAR),
                 file_info->FileName);
 
               filenamew[size - 1] = L'\0';