Configurable transport parameters.

Configurable transport parameters.

 - integer parameters can be configured using the following directives:

    quic_max_idle_timeout
    quic_max_ack_delay
    quic_max_packet_size
    quic_initial_max_data
    quic_initial_max_stream_data_bidi_local
    quic_initial_max_stream_data_bidi_remote
    quic_initial_max_stream_data_uni
    quic_initial_max_streams_bidi
    quic_initial_max_streams_uni
    quic_ack_delay_exponent
    quic_active_migration
    quic_active_connection_id_limit

 - only following parameters are actually sent:

    active_connection_id_limit
    initial_max_streams_uni
    initial_max_streams_bidi
    initial_max_stream_data_bidi_local
    initial_max_stream_data_bidi_remote
    initial_max_stream_data_uni

 (other parameters are to be added into ngx_quic_create_transport_params()
  function as needed, should be easy now)

 - draft 24 and draft 27 are now supported
   (at compile-time using quic_version macro)