[ticket/12829] Remove check for pgsql 8.3/8.2

Remove check for pgsql 8.3/8.2 and set multi_insert to true.

PHPBB3-12829
Merge pull request #2711 from n-aleha/ticket/12829

[ticket/12829] Remove check for pgsql 8.3/8.2

* n-aleha/ticket/12829:
  [ticket/12829] Remove check for pgsql 8.3/8.2