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/Driver/Job.cpp b/lib/Driver/Job.cpp
index 38f68eb..42cc1bc 100644
--- a/lib/Driver/Job.cpp
+++ b/lib/Driver/Job.cpp
@@ -41,7 +41,7 @@
     .Cases("-internal-externc-isystem", "-iprefix", "-iwithprefix", true)
     .Cases("-iwithprefixbefore", "-isysroot", "-isystem", "-iquote", true)
     .Cases("-resource-dir", "-serialize-diagnostic-file", true)
-    .Case("-dwarf-debug-flags", true)
+    .Cases("-dwarf-debug-flags", "-ivfsoverlay", true)
     .Default(false);
 
   // Match found.