Existing scripts detecting https see a change in results

E.g. Auth CAS SSL detection problem

This is a regression from MDL-28484.

auth cas has it's own custom _isHttps function which checks
$_SERVER['HTTP_X_FORWARDED_PROTO']
$_SERVER['HTTPS']
$_SERVER['SERVER_PORT']
$_SERVER['HTTP_X_FORWARDED_PORT']

I'm not worried about updating auth_cas to use the new function, I am worried that adding the function caused a regression in existing scripts (and hence all third party scripts).