windows: use unsafe.Slice in (*RawSockaddrAny).Sockaddr on windows

Same as CL 472035 did in package syscall.

Change-Id: I153dfaa19933a2707848e4183d6ca704c2800a0e
Reviewed-on: https://go-review.googlesource.com/c/sys/+/472016
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

windows/syscall_windows.go

@@ -1022,8 +1022,7 @@ func (rsa *RawSockaddrAny) Sockaddr() (Sockaddr, error) {
 		for n < len(pp.Path) && pp.Path[n] != 0 {
 			n++
 		}
-		bytes := (*[len(pp.Path)]byte)(unsafe.Pointer(&pp.Path[0]))[0:n]
-		sa.Name = string(bytes)
+		sa.Name = string(unsafe.Slice((*byte)(unsafe.Pointer(&pp.Path[0])), n))
 		return sa, nil
 
 	case AF_INET: