BUILD: ssl: unbreak the build with newer libressl

In LibreSSL 3.5.0, BIO is going to become opaque, so haproxy's
compat macros will no longer work. The functions they substitute
have been available since LibreSSL 2.7.0.
diff --git a/include/haproxy/openssl-compat.h b/include/haproxy/openssl-compat.h
index 17d073d..123b76e 100644
--- a/include/haproxy/openssl-compat.h
+++ b/include/haproxy/openssl-compat.h
@@ -417,7 +417,7 @@
 #define SSL_CTX_get_extra_chain_certs(ctx, chain) do { *(chain) = (ctx)->extra_certs; } while (0)
 #endif
 
-#if HA_OPENSSL_VERSION_NUMBER < 0x10100000L
+#if HA_OPENSSL_VERSION_NUMBER < 0x10100000L && (!defined(LIBRESSL_VERSION_NUMBER) || LIBRESSL_VERSION_NUMBER < 0x2070000fL)
 #define BIO_get_data(b)            (b)->ptr
 #define BIO_set_data(b, v)         do { (b)->ptr  = (v); } while (0)
 #define BIO_set_init(b, v)         do { (b)->init = (v); } while (0)