v5.6.0

Main Changes to previous release version:

• Add bulk-message receipt testcases;
• Remove compilation error for windows platform;
• Add express node config;
• Add speed meter for express service node;
• Update dependency LIBCURL and enable SSL for express server;
• Add friend receipt testcases and several bug-fixes;
• Improving implementation of offmsg/offreq/offreceipt callbacks;
• Improving configure express nodes and removing original hive bootstrap configuration.
• improving function 'on_friend_message_receipt' and remove useless internal functions.
• Improve generate_msgid and internal dht_friend_message functions.
• Improve implementation of common function 'send_friend_message_internal' and internal called functions.
• Improve implementation of receipt acknowledge.
• convert receipt list to hash-table and bug-fixes.
• Combine send message and send receipt message.
• Add express, post/pull/delete offline message, request/onrequest friend.