Update Clang for rebase to r212749.

This also fixes a small issue with arm_neon.h not being generated always.

Includes a cherry-pick of:
r213450 - fixes mac-specific header issue
r213126 - removes a default -Bsymbolic on Android

Change-Id: I2a790a0f5d3b2aab11de596fc3a74e7cbc99081d
diff --git a/test/OpenMP/simd_linear_messages.cpp b/test/OpenMP/simd_linear_messages.cpp
index e90bc69..b8b7831 100644
--- a/test/OpenMP/simd_linear_messages.cpp
+++ b/test/OpenMP/simd_linear_messages.cpp
@@ -50,10 +50,11 @@
   // expected-error@+1 {{argument of a linear clause should be of integral or pointer type}}
 #pragma omp simd linear(ind2:L)
   for (i = 0; i < num; ++i) {
-    T cur = arr[ind2];
+    T cur = arr[(int)ind2];
     ind2 += L;
     sum += cur;
   }
+  return T();
 }
 
 template<int LEN> int test_warn() {