Synchronize LLVM's copy of libc++abi's demangler with the libc++abi
version after r371273.

Also fix a minor issue in r371273 that only surfaced after template
instantiation from LLVM's use of the demangler.

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@371274 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/demangle/ItaniumDemangle.h b/src/demangle/ItaniumDemangle.h
index f5bb0d6..c1efd7e 100644
--- a/src/demangle/ItaniumDemangle.h
+++ b/src/demangle/ItaniumDemangle.h
@@ -2435,7 +2435,8 @@
     ParsingLambdaParamsAtLevel = (size_t)-1;
     TryToParseTemplateArgs = true;
     PermitForwardTemplateReferences = false;
-    NumSyntheticTemplateParameters = {};
+    for (int I = 0; I != 3; ++I)
+      NumSyntheticTemplateParameters[I] = 0;
     ASTAllocator.reset();
   }