AST: Briefly consider sort{} cases
AST: First stab at exposing sort in most of its variants

"reverse sort" is still buggy because of garbage OP tree surrounding
the final sort.
Not all sort flags are exposed (use integer, the various sort algos, etc).
Debatable: A sort using a named sub exposes the named sub just as a string
(constant).
AST: Extra sort test case
Silence warning