Bound JSON-RPC input by size and nesting depth

Enforce the nesting bound in one parse, capping allocation by depth, not input size.

src/rpc/rpc_manager.cc

@@ -176,6 +176,7 @@ RpcManager::set_size_limit(uint64_t size) {
     throw torrent::input_error("XMLRPC size limit is too small to hold a request.");
 
   m_xmlrpc.set_size_limit(size);
+  m_jsonrpc.set_size_limit(size);
 }
 
 void