Maximum sound duration check?

[PotcFdk]

So this commit gave me an idea:

How about adding a configurable maximum sound duration check to the preprocessor?
It would check all files if they are longer than X seconds, and if so, they would be marked as invalid unless they are explicitly whitelisted somewhere.

The possible advantages:

• Makes it harder for accidental mistakes in editing to go unnoticed
  (I've committed the entire audio stream instead of just the correct part before and didn't notice it for quite some time)
• Forcing people to explicitly whitelist costs more willpower/effort -> more careful consideration -> reduced amount of overlong sounds
• A whitelist makes it easy to see, inspect, audit and re-consider the violations