* Revert r94487 and r19889 to an extent -- ONLY check for the X-Forwarded-For header...

* Revert r94487 and r19889 to an extent -- ONLY check for the X-Forwarded-For header when we are behind a proxy, as mostly every properly configured proxy software sets it, and attempting to support those that do not opens up the ability to spoof IP addresses by setting arbitrary headers.