change the message_queue and subscribers_queue type on the ngx_http_push_stream_worker_data_t structure

not sending the access control headers by default, send only when the allowed_origins directive is set

add the number of stored messages and the number of channels and messages in the trash to summarized channels statistics

renaming the queue of messages to be removed from the memory and changing the way the queue is cleared

avoiding segmentation fault by access a null reference on a tree node, after be removed by another worker