[ABI/Metadata] Add @autoclosure to function parameter flags

Add `@autoclosure` to parameter flags associated with
function type metadata, which makes it possible to correctly
round-trip mangled name <-> metadata of function types which
have parameters marked as `@autoclosure`.

Resolves: rdar://problem/45489901

lib/RemoteAST/RemoteAST.cpp

@@ -365,7 +365,8 @@ public:
       auto ownership = flags.getValueOwnership();
       auto parameterFlags = ParameterTypeFlags()
                                 .withValueOwnership(ownership)
-                                .withVariadic(flags.isVariadic());
+                                .withVariadic(flags.isVariadic())
+                                .withAutoClosure(flags.isAutoClosure());
 
       funcParams.push_back(AnyFunctionType::Param(type, label, parameterFlags));
     }