File.Open_flagFlags for use with Luv.File.open_. See the flags in open(3p).
type t = [ | `RDONLY| `WRONLY| `RDWR| `CREAT| `EXCL| `EXLOCK| `NOCTTY| `NOFOLLOW| `TEMPORARY| `TRUNC| `APPEND| `DIRECT| `DSYNC| `FILEMAP| `NOATIME| `NONBLOCK| `RANDOM| `SEQUENTIAL| `SHORT_LIVED| `SYMLINK| `SYNC ]`FILEMAP requires libuv 1.31.0.
Feature check: Luv.Require.(has fs_o_filemap)