v6.0.1

Main Changes to previous release version:

• Bugfix for internal dependency library: libcurl;
• Upgraded to the almost latest versions for internal dependency libraries: libcrystal/pjsip/toxcore;
• Add checking mechanism for consistency of internal persistent data before creating carrier instance;
• Checking thread reentrancy safety for internal library use;
• Bugfixes for api-tests test cases, especially the synchronization between tests and test-robot;
• Improvements on message delivery confirmation in the edge case that friends become offline or were removed.
• Improvements on the message-id generation mechanism, where now globally managed the message-id for all online and offline messages both;
• Implemented the new extension module to unify the layer for extension modules, such as session, file-transfer, and WebRTC wrapper;
• Refactored all APIs name with the new prefix "carrier-" instead of "ela-" to make it more official as Carrier service, but still keep the original APIs as deprecated APIs for original use;
• Refactored the libraries name with the prefix "libcarrier" instead of "libela-*;
• Removed the deprecated API: int ela_send_friend_message(ElaCarrier *carrier, const char *to, constvoid *message, size_t len, bool *offline);