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/lib/Basic/Version.cpp b/lib/Basic/Version.cpp
index ae32c01..c2b7753 100644
--- a/lib/Basic/Version.cpp
+++ b/lib/Basic/Version.cpp
@@ -13,7 +13,7 @@
 
 #include "clang/Basic/Version.h"
 #include "clang/Basic/LLVM.h"
-#include "llvm/Config/config.h"
+#include "clang/Config/config.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstdlib>
 #include <cstring>
@@ -130,7 +130,7 @@
 
   // If vendor supplied, include the base LLVM version as well.
 #ifdef CLANG_VENDOR
-  OS << " (based on LLVM " << PACKAGE_VERSION << ")";
+  OS << " (based on " << BACKEND_PACKAGE_STRING << ")";
 #endif
 
   return OS.str();