CRM-13805 - Set a status alert if cURL is not installed.

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* CRM-13805: Fetching CiviCRM News fails silently if cURL is not installed
  http://issues.civicrm.org/jira/browse/CRM-13805
Merge pull request #2058 from fjg-conflux/CRM-13805

CRM-13805 - Set a status alert if cURL is not installed.