Removed #define LSQUIC_SUPPORTS_CONNCLOSEFRAME_CALLBACK

See discussion in PR #205

Author: Dmitri Tikhonov

include/lsquic.h

@@ -227,7 +227,6 @@ struct lsquic_stream_if {
      * errors received with the CONNECTION_CLOSE frame. If app_error is -1 then
      * it is considered unknown if this is an app_error or not.
      */
-#define LSQUIC_SUPPORTS_CONNCLOSEFRAME_CALLBACK
     void (*on_conncloseframe_received)(lsquic_conn_t *c,
                                        int app_error, uint64_t error_code,
                                        const char *reason, int reason_len);