devel/libcdada: new port in prepartion for net-mgmt/pmacct update

Small library that offers basic data structures (list, set, map...)
in a pure C API for user-space applications. Key features:

• Easy to use, portable
• No "magic" MACROs, and no need to modify your data structures (except, perhaps, for attribute((packed)))
• Stable and well-tested backend engine (libstdc++) for most of the data structures
• Reasonable performance - comparable to libstdc++