Fixes core dump when reusing thread when running debug binary


sql-bench/bench-init.pl.sh:
  Use ENGINE= instead of TYPE=
sql-bench/server-cfg.sh:
  Use ENGINE= instead of TYPE=
sql/mysqld.cc:
  Set thread_stack (to avoid core dump in store_globlas)
sql/sql_parse.cc:
  Set thread_stack after return from end_thread()