CVE-2024-2398: HTTP/2 push headers memory-leak

Summary: For each incoming `PUSH_PROMISE` header a new `name:value` string is allocated and the pointer to that string is stored in the `stream->push_headers` array.

h = aprintf("%s:%s", name, value);
    if(h)
      stream->push_headers[stream->push_headers_used++] = h;