fixes #996 escape word "groups" in SQL queries, new reserved word with MySQL 8

admin/include/functions.php

@@ -2438,7 +2438,7 @@ function get_groupname($group_id)
 {
   $query = '
 SELECT name
-  FROM '.GROUPS_TABLE.'
+  FROM `'.GROUPS_TABLE.'`
   WHERE id = '.intval($group_id).'
 ;';
   $result = pwg_query($query);
@@ -3022,7 +3022,7 @@ SELECT CONCAT(
     "_",
     COUNT(*)
   )
-  FROM '. $tables[$item] .'
+  FROM `'. $tables[$item] .'`
 ;';
     list($keys[$item]) = pwg_db_fetch_row(pwg_query($query));
   }