Fix node order when we demangle opaque types.

When we formed a mangled name key to look up opaque return type decls during
interface parsing, we were accidentally including the `Global` demangle node
inside the `OpaqueReturnTypeOf` node, which ended up including the `$s` prefix
in the mangling. Other type reconstruction clients like lldb which provided
well-formed mangling trees did not include the Global node, causing the prefix
to get left off and lookups to fail. Fix Sema to remove the Global node before
looking up the opaque type, and have type reconstruction consistently apply the
prefix to the lookup key.

Author: jckarter

lib/AST/ASTDemangler.cpp

@@ -255,11 +255,14 @@ Type ASTBuilder::resolveOpaqueType(NodePointer opaqueDescriptor,
                                    unsigned ordinal) {
   if (opaqueDescriptor->getKind() == Node::Kind::OpaqueReturnTypeOf) {
     auto definingDecl = opaqueDescriptor->getChild(0);
-    auto mangledName = mangleNode(definingDecl);
+    auto definingGlobal = Factory.createNode(Node::Kind::Global);
+    definingGlobal->addChild(definingDecl, Factory);
+    auto mangledName = mangleNode(definingGlobal);
+    
     auto moduleNode = findModuleNode(definingDecl);
     if (!moduleNode)
       return Type();
-    auto parentModule = findModule(findModuleNode(definingDecl));
+    auto parentModule = findModule(moduleNode);
     if (!parentModule)
       return Type();
 

lib/Sema/TypeCheckType.cpp

@@ -2481,6 +2481,8 @@ Type TypeResolver::resolveOpaqueReturnType(TypeRepr *repr,
   auto definingDeclNode = demangle.demangleSymbol(mangledName);
   if (!definingDeclNode)
     return Type();
+  if (definingDeclNode->getKind() == Node::Kind::Global)
+    definingDeclNode = definingDeclNode->getChild(0);
   ASTBuilder builder(Context);
   builder.Resolver = resolution.Resolver;
   auto opaqueNode =