CRM-14210. Use get_headers() and check for 200 response instead of file_get_contents(), as some servers do not return FALSE on 40x response code.
CRM-14210 - Add hidden option to disable security alerts
CRM_Utils_Check_Security - Represent messages as objects
CRM-14210 - Add API for running security checks
Merge pull request #2631 from totten/4.4-14210

CRM-14210 - Use get_headers(). Add API.