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/Tooling/CompilationDatabase.cpp b/lib/Tooling/CompilationDatabase.cpp
index 94bdc8d..4b776bf 100644
--- a/lib/Tooling/CompilationDatabase.cpp
+++ b/lib/Tooling/CompilationDatabase.cpp
@@ -27,8 +27,8 @@
 #include "llvm/Option/Arg.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/Path.h"
-#include "llvm/Support/system_error.h"
 #include <sstream>
+#include <system_error>
 
 namespace clang {
 namespace tooling {