adding proof of context-sensitivy of raw string literals

Stumbled across this and thought it would be cool to prove. I've never used Ogden's Lemma before, but I'm pretty sure I used it right. The pumping lemma definitely doesn't seem sufficient for the job. In particular, when using the pumping lemma, you can always just pump one of the quotes, and it's fine. Ogden's Lemma lets you effectively force the pumper to use certain characters in the string.

@cmr
Okay, at this point I buy the reasoning presented below.

Therefore, I see no reason to keep the sentence "I (cmr) know of no way to resolve this."

Delete that, and address the other comments I left, and I think we will be good to go.