windows: add various NT APIs

In anticipation of the next commit which adds win32 pipe APIs, add some
of the foundational NT APIs for that, which will be required for making
a robust Go pipe library. Also add a simple test case.

Change-Id: I898bd6c5265a8939a7f05a24c4d9b22941dc56b7
Reviewed-on: https://go-review.googlesource.com/c/sys/+/298171
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

windows/security_windows.go

@@ -908,6 +908,19 @@ type SECURITY_DESCRIPTOR struct {
 	dacl     *ACL
 }
 
+type SECURITY_QUALITY_OF_SERVICE struct {
+	Length              uint32
+	ImpersonationLevel  uint32
+	ContextTrackingMode byte
+	EffectiveOnly       byte
+}
+
+// Constants for the ContextTrackingMode field of SECURITY_QUALITY_OF_SERVICE.
+const (
+	SECURITY_STATIC_TRACKING  = 0
+	SECURITY_DYNAMIC_TRACKING = 1
+)
+
 type SecurityAttributes struct {
 	Length             uint32
 	SecurityDescriptor *SECURITY_DESCRIPTOR