avoid respawning iconv all the time

examples/dvb_print_si.c

@@ -163,6 +163,7 @@ static char *iconv_wrapper(void *_unused, const char *psz_encoding,
                 psz_native_encoding);
         return iconv_append_null(p_string, i_length);
     }
+    psz_current_encoding = psz_encoding;
 
     /* converted strings can be up to six times larger */
     i_out_length = i_length * 6;