Check for missing 'Pending' membership status during upgrade to 3.1.4 and insert if not there

Current versions of CiviCRM set Pending membership status to reserved so it can't be edited or deleted. However, some upgraded sites are missing the 'Pending' membership status. We should check for it in the 3.1.4 incremental upgrade, and insert if missing since we throw fatal error if not present.

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This is due to line 695-ish in Core_BAO_Membership.php

$pendingStatusId = array_search( 'Pending', CRM_Member_PseudoConstant::membershipStatus( ) );

One option is just to make the membership status pending un-editable through CiviCRM

UPDATE `civicrm_membership_status` SET `is_admin` = '1' WHERE `civicrm_membership_status`.`name` = 'Pending' LIMIT 1;