- serialize.h/c: universal binary serialization for structures with
variable-length fields (ASCIIZ, ARRAY) using pointers
- Auto allocation via u_malloc during deserialization
- Support for header (arbitrary bytes at buffer start)
- serialize_encode(): serialize structure to buffer
- serialize_decode(): deserialize from buffer (without header)
- serialize_free(): free structure and all its pointers
- tests/test_serialize.c: unit tests