Add basic check for the runtime environment

Add basic check for the runtime environment

Running WoltLab Suite in an unsupported environment might work for the
majority of requests, some requests might fail very visibly. But there
also is a third type: A request that *appear* to execute properly, but
that subtly behaves incorrectly, due to a change in PHP's behavior.

The latter type is dangerous, as those requests might introduce errors
into the dataset that are very hard to impossible to correct after the
fact because the necessary information to fix up the data is no longer
available.

Prevent this situation from occuring by performing a basic test of the
runtime environment and halting processing early if this test fails to
ensure that it processed as little as possible.