[Fixes #75802914] Allow whitespace in X-Forwarded-For

The draft specification, which is probably the best we'll ever have, says
that whitespace between values is optional:

- http://tools.ietf.org/html/draft-ietf-appsawg-http-forwarded-10#section-7.1

Although it's quite common for there to be spaces, CloudFlare and some other
reverse-proxies don't add them, and it's even more common for software that
reads the header to do a split+trim.

So relax this test by checking the total number of values and then the value
of each after stripping whitespace.
I'm not sure how to do it without cluttering the output.

You will get two errors if both are incorrect, if that helps?