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/CacheTokens.cpp b/lib/Frontend/CacheTokens.cpp
index d30196d..14f7027 100644
--- a/lib/Frontend/CacheTokens.cpp
+++ b/lib/Frontend/CacheTokens.cpp
@@ -540,7 +540,8 @@
   ~StatListener() {}
 
   LookupResult getStat(const char *Path, FileData &Data, bool isFile,
-                       vfs::File **F, vfs::FileSystem &FS) override {
+                       std::unique_ptr<vfs::File> *F,
+                       vfs::FileSystem &FS) override {
     LookupResult Result = statChained(Path, Data, isFile, F, FS);
 
     if (Result == CacheMissing) // Failed 'stat'.