* "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"