Mudlib strlen fix

Saw the note about the deprecation of `strlen` and figured I would go ahead and replace it in the mudlib files. each file is a separate commit, so you can use cherry pick to take the ones you need if I was overzealous.

I did _not_ change the instances of `strlen` in uni-crasher.

My editor is configured to remove end-of-line whitespace, so there are a few more lines changed than what I actually modified.