CRM-14354 - Fixes bug in which user selects recurring membership but database records it as non-recurring. Appears to be an edge case (contribution form must be configured to separate contributions, the additional contribution field set to accept any amount, and the additional amount blank). Pretty much reverses CRM-3781, but we *DO* now support recurring membership payments.

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* CRM-14354: Additional gift breaks ARB (auto-renewing) memberships
  http://issues.civicrm.org/jira/browse/CRM-14354
* CRM-3781: Memberships charges are set to recurring if an additional recurring contribution is selected
  http://issues.civicrm.org/jira/browse/CRM-3781