db_drop_field() is not working with MySQL reserved words

This is related to 🐛 DatabaseSchema_mysql::fieldExists() does not escape the column name Needs review . The issue is caused by DatabaseSchema_mysql::fieldExists(), which is called by DatabaseSchema_mysql::dropField().

public function fieldExists($table, $column) {
  // The information_schema table is very slow to query under MySQL 5.0.
  // Instead, we try to select from the table and field in question. If it
  // fails, the most likely reason is that it does not exist. That is
  // dramatically faster than using information_schema.
  // @link http://bugs.mysql.com/bug.php?id=19588
  // @todo: This override should be removed once we require a version of MySQL
  // that has that bug fixed.
  try {
    $this->connection->queryRange("SELECT {$column} FROM {" . $table . "}", 0, 1);
    return TRUE;
  } catch (Exception $e) {
    return FALSE;
  }
}

Once that issue is fixed, this issue will be fixed too.