Improve checking the use of SSL
Improve checking the use of SSL

Servers that are behind a proxy will always have `%{HTTPS} === off`.
To prevent infinite redirect loops in this scenario this commit adds a
check on the
[X-Forwarded-Proto](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-Proto)
header before defaulting back to the `%{HTTPS}` check. This should cover
about 99% of possible htaccess/ssl related scenarios.

jonasdekeukelaere/forkcms,carakas/forkcms,carakas/forkcms,jessedobbelaere/forkcms,jessedobbelaere/forkcms,sumocoders/forkcms,bartdc/forkcms,forkcms/forkcms,sumocoders/forkcms,forkcms/forkcms,jonasdekeukelaere/forkcms,carakas/forkcms,jonasdekeukelaere/forkcms,jacob-v-dam/forkcms,jessedobbelaere/forkcms,bartdc/forkcms,jessedobbelaere/forkcms,jacob-v-dam/forkcms,Katrienvh/forkcms,justcarakas/forkcms,justcarakas/forkcms,jacob-v-dam/forkcms,sumocoders/forkcms,carakas/forkcms,sumocoders/forkcms,carakas/forkcms,bartdc/forkcms,jonasdekeukelaere/forkcms,Katrienvh/forkcms,forkcms/forkcms,jacob-v-dam/forkcms,jonasdekeukelaere/forkcms,Katrienvh/forkcms,justcarakas/forkcms,Katrienvh/forkcms,forkcms/forkcms,sumocoders/forkcms