Certain groups of web proxies do not set these values properly.  Notably,
proxies for cell phones, which often do not set the remote IP information
correctly (not surprisingly, since the clients do not have an IP address).

Allowing this to be configurable makes it possible for developers to choose
to ignore this simple spoofing check, when a significant amount of their
traffic would result in false positives anyway.
Signed-off-by: NMichael Koziarski <michael@koziarski.com>

[#1200 state:committed]