Deal with initial_scid, retry_scid, and original_dcid.  We need to set
and get QUIC transport parameters timely manner.  Therefore, transport
parameter operations are now done by ngtcp2_crypto library.
Applications do not need to do set it manually.  Added several
callback function implementations to ngtcp2_crypto library which can
be directly passed to ngtcp2_callbacks: client_initial, recv_retry,
and recv_client_initial.  Installation of initial packet number space
encryption keys is now handled by ngtcp2_crypto library.  They are
done in ngtcp2_crypto_client_initial_cb, ngtcp2_crypto_recv_retry_cb
and ngtcp2_crypto_recv_client_initial_cb.

Commit 0999d327 ("Pass user-defined
printf function rather than passing file descriptor") removed the usage
of errno so it does not need to be included.

ngtcp2_connection_close.reason_len is size_t, which is not necessarily 64-bit.

The changed semantics will be implemented in the later commits.

Adding the final newline is left to the logging implementation.