Use switch operator[](int) to kth<int>() so we can use vget_lane.

tests/SkNxTest.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkNx.h"
 #include "Test.h"
 
 template <int N, typename T>
 static void test_Nf(skiatest::Reporter* r) {
 
     auto assert_nearly_eq = [&](double eps, const SkNf<N,T>& v, T a, T b, T c, T d) {
         auto close = [=](T a, T b) { return fabs(a-b) <= eps; };
         T vals[4];
         v.store(vals);
-        REPORTER_ASSERT(r, close(vals[0], a) && close(vals[1], b));
-        REPORTER_ASSERT(r, close(   v[0], a) && close(   v[1], b));
-
+        bool ok = close(vals[0], a) && close(vals[1], b)
+               && close(v.template kth<0>(), a) && close(v.template kth<1>(), b);
+        REPORTER_ASSERT(r, ok);
         if (N == 4) {
-            REPORTER_ASSERT(r, close(vals[2], c) && close(vals[3], d));
-            REPORTER_ASSERT(r, close(   v[2], c) && close(   v[3], d));
+            ok = close(vals[2], c) && close(vals[3], d)
+              && close(v.template kth<2>(), c) && close(v.template kth<3>(), d);
+            REPORTER_ASSERT(r, ok);
         }
     };
     auto assert_eq = [&](const SkNf<N,T>& v, T a, T b, T c, T d) {
         return assert_nearly_eq(0, v, a,b,c,d);
     };
 
     T vals[] = {3, 4, 5, 6};
     SkNf<N,T> a = SkNf<N,T>::Load(vals),
               b(a),
               c = a;
@@ skipping 35 matching lines @@
     REPORTER_ASSERT(r, !(a >= fours).allTrue());
 }
 
 DEF_TEST(SkNf, r) {
     test_Nf<2, float>(r);
     test_Nf<2, double>(r);
 
     test_Nf<4, float>(r);
     test_Nf<4, double>(r);
 }