Addresses two issues:
1. When pgsql extension is missing, @pg_connect would silently
abort execution. Check for pg_connect existence before calling it,
same with pg_pconnect.
2. When connection fails, the error reported by php is discarded.
User is shown the failure message without the reason for failure,
making debugging difficult. Collect the error (if any) via a
temporarily installed error handler, and display it if connection
failed.
PHPBB3-10057
d69a7c620a