Update more uses of Option, Some and None to camel case

I've updated most of the outstanding lowercase uses of Option, Some and None. I was inspired by the error message (corrected in 7ff7489dc62bdcc0dbd507c52cba90d47cfdd129) as it was slightly misleading.

There are still outstanding uses of the lowercase None. If this is useful, I'll go back and work through that list as well.

I haven't added any new regression tests. I wasn't sure they were appropriate in this case. Almost all of these changes are to places that the tests don't really cover: comments, xfailed tests and error and debug messages.

make check: summary of 23 test runs: 4252 passed; 0 failed; 280 ignored :)