* "in_" and "not_in" should coerce their results to strings (i.e., chr(result))
* TestLeftrec: success case 2 fails
* TestChRange: success case segfaults
* TestWhitespaceEnd: success case segfaults
* TestAction: success case segfaults with "corrupted double-linked list"
* TestButNotRange: segfaults, probably because of whatever's wrong with ch_range
* TestXor: segfaults; failure case craps out with "malloc(): smallbin double linked list corrupted"