windows: add WTSGetActiveConsoleSessionId

https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-wtsgetactiveconsolesessionid

Change-Id: I3c180bbb3a768beac6633e78514fac4e3837b69d
Reviewed-on: https://go-review.googlesource.com/c/sys/+/331909
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Trust: Brad Fitzpatrick <bradfitz@golang.org>
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/windows/zsyscall_windows.go b/windows/zsyscall_windows.go
index 148de0f..2083ec3 100644
--- a/windows/zsyscall_windows.go
+++ b/windows/zsyscall_windows.go
@@ -346,6 +346,7 @@
 	procVirtualLock                                          = modkernel32.NewProc("VirtualLock")
 	procVirtualProtect                                       = modkernel32.NewProc("VirtualProtect")
 	procVirtualUnlock                                        = modkernel32.NewProc("VirtualUnlock")
+	procWTSGetActiveConsoleSessionId                         = modkernel32.NewProc("WTSGetActiveConsoleSessionId")
 	procWaitForMultipleObjects                               = modkernel32.NewProc("WaitForMultipleObjects")
 	procWaitForSingleObject                                  = modkernel32.NewProc("WaitForSingleObject")
 	procWriteConsoleW                                        = modkernel32.NewProc("WriteConsoleW")
@@ -2992,6 +2993,12 @@
 	return
 }
 
+func WTSGetActiveConsoleSessionId() (sessionID uint32) {
+	r0, _, _ := syscall.Syscall(procWTSGetActiveConsoleSessionId.Addr(), 0, 0, 0, 0)
+	sessionID = uint32(r0)
+	return
+}
+
 func waitForMultipleObjects(count uint32, handles uintptr, waitAll bool, waitMilliseconds uint32) (event uint32, err error) {
 	var _p0 uint32
 	if waitAll {