moved LIMIT initialialization, because it is need only for single select derived table


mysql-test/r/derived.result:
  test suite for BUG#2349
mysql-test/t/derived.test:
  test suite for BUG#2349
sql/sql_derived.cc:
  assigned correct lex->current_select (BUG#2349)
  moved LIMIT initialialization, because it is need only for single select