Update aosp/master Clang with patches for fp16

Cherry-pick Clang revision r237406

Change-Id: I8670bec201bf76b426495884ed80b9280ac85023
(cherry picked from commit e9a54b6cc25f564aa5c99b62e888e484cede3959)
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index da1a088..d2b528c 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1570,7 +1570,7 @@
   Opts.ImplementationOfModule =
       Args.getLastArgValue(OPT_fmodule_implementation_of);
   Opts.ModuleFeatures = Args.getAllArgValues(OPT_fmodule_feature);
-  Opts.NativeHalfType = Opts.NativeHalfType;
+  Opts.NativeHalfType |= Args.hasArg(OPT_fnative_half_type);
   Opts.HalfArgsAndReturns = Args.hasArg(OPT_fallow_half_arguments_and_returns);
   Opts.GNUAsm = !Args.hasArg(OPT_fno_gnu_inline_asm);