Silence coucal hashtable stats on the default log handler

coucal_delete() logs a per-table stats summary at info level. For tables
without their own handler (webhttrack's NewLangStr/NewLangStrKeys), these
went through default_coucal_loghandler, which printed every level, so
plain `webhttrack` startup dumped two "hashtable ... summary:" lines to
the console.

Drop info-and-below messages there unless debugging is on (hts_dgb_init,
i.e. HTS_LOG / hts_debug); warnings and critical errors still always
print.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

src/htslib.c

@@ -5305,6 +5305,11 @@ static int get_loglevel_from_coucal(coucal_loglevel level) {
 static void default_coucal_loghandler(void *arg, coucal_loglevel level, 
                                        const char* format, va_list args) {
 
+  /* informational chatter (hashtable stats on delete, etc.) only when
+     debugging; keep warnings and critical errors always visible. */
+  if (level > coucal_log_warning && hts_dgb_init <= 0) {
+    return;
+  }
   if (level <= coucal_log_warning) {
     fprintf(stderr, "** warning: ");
   }