Local code execution via schema error handling

Stack-based buffer overflow in flatcc 0.6.0 allows local users to execute arbitrary code by compiling a crafted schema file. In parser.c, error_ref_sym decrements a zero size_t after filling its fixed stack buffer, wraps the remaining-length counter, and then copies more identifier text past the buffer. Exploitation requires local access to invoke the flatcc compiler with a malicious schema and can crash the process or run code in the compiler's security context.