Revert "Revert "Upgrade to 5.0.71.48"" DO NOT MERGE

This reverts commit f2e3994fa5148cc3d9946666f0b0596290192b0e,
and updates the x64 makefile properly so it doesn't break that
build.

FPIIM-449

Change-Id: Ib83e35bfbae6af627451c926a9650ec57c045605
(cherry picked from commit 109988c7ccb6f3fd1a58574fa3dfb88beaef6632)
diff --git a/third_party/llvm-build/Release+Asserts/lib/clang/3.9.0/include/xtestintrin.h b/third_party/llvm-build/Release+Asserts/lib/clang/3.9.0/include/xtestintrin.h
new file mode 100644
index 0000000..9d3378f
--- /dev/null
+++ b/third_party/llvm-build/Release+Asserts/lib/clang/3.9.0/include/xtestintrin.h
@@ -0,0 +1,41 @@
+/*===---- xtestintrin.h - XTEST intrinsic ---------------------------------===
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ *===-----------------------------------------------------------------------===
+ */
+
+#ifndef __IMMINTRIN_H
+#error "Never use <xtestintrin.h> directly; include <immintrin.h> instead."
+#endif
+
+#ifndef __XTESTINTRIN_H
+#define __XTESTINTRIN_H
+
+/* xtest returns non-zero if the instruction is executed within an RTM or active
+ * HLE region. */
+/* FIXME: This can be an either or for RTM/HLE. Deal with this when HLE is
+ * supported. */
+static __inline__ int
+    __attribute__((__always_inline__, __nodebug__, __target__("rtm")))
+    _xtest(void) {
+  return __builtin_ia32_xtest();
+}
+
+#endif