BUILD: quic: Fix build error when building QUIC against libressl.

BUILD: quic: Fix build error when building QUIC against libressl.

This previous commit was not sufficient to completely fix the building issue
in relation with the TLS stack 0-RTT support. LibreSSL was the last TLS
stack to refuse to compile because of undefined a QUIC specific function
for 0-RTT: SSL_set_quic_early_data_enabled().

To get rid of such compilation issues, define HA_OPENSSL_HAVE_0RTT_SUPPORT
only when building against TLS stack with 0-RTT support.

No need to backport.