[boost] Announcing LEAF, a new error handling library suitable for low latency applications

LEAF (Low-latency Error Augmentation Framework) is a new error handling library which could possibly become the successor of Boost Exception, though LEAF can be used without exceptions too. Official documentation: https://zajo.github.io/leaf/ Features: - No dynamic memory allocations. - Associate objects of arbitrary types with any failure -- when it is initially reported or at a later time. - Compatible with std::error_code, errno and any other error handling API. - Use with or without exception handling. - Support for multi-thread programming. Emil