Set secure flags when opening a named pipe on Windows
Fixes https://github.com/rust-lang/rust/issues/42036, see also the previous attempt in https://github.com/rust-lang/rust/pull/44556.
Whether this is correct depends on if it is somehow possible to create a symlink to a named pipe, outside the named pipe filesystem (NPFS). But as far as I can tell that should be impossible.
Also fixes that `security_qos_flags(SECURITY_ANONYMOUS)` does not set the `SECURITY_SQOS_PRESENT` flag, and the incorrect documentation about the default value of `security_qos_flags`.