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/Frontend/CreateInvocationFromCommandLine.cpp b/lib/Frontend/CreateInvocationFromCommandLine.cpp
index 45f7aa3..f2f36e4 100644
--- a/lib/Frontend/CreateInvocationFromCommandLine.cpp
+++ b/lib/Frontend/CreateInvocationFromCommandLine.cpp
@@ -32,7 +32,7 @@
 CompilerInvocation *
 clang::createInvocationFromCommandLine(ArrayRef<const char *> ArgList,
                             IntrusiveRefCntPtr<DiagnosticsEngine> Diags) {
-  if (!Diags.getPtr()) {
+  if (!Diags.get()) {
     // No diagnostics engine was provided, so create our own diagnostics object
     // with the default options.
     Diags = CompilerInstance::createDiagnostics(new DiagnosticOptions);