Add keyed lists and text comparison

A list state may name a key field of its record (the flags word of its
entry: field + 1). A keyed list keeps its items in key order, numbers by
value and texts by their bytes, each key once: LIST_APPEND places an item
by halving and fails with the new fault exists (PURE_CONFLICT) when the
key is there; LIST_FIND gives the index of a key's item and LIST_HAS
whether it is there. The verifier refuses inserting by position and
changing a key. Maps, sets and sorted maps are one list with an order
rule, so tables, filters, folds, indices, storage and replacement stay
as they are.

A module that opens over a list not in its key order (one that was not
keyed, keyed by another field, or stored so) puts it in order, moves its
indices with their items and stores it again; two items with one key
refuse the module rather than drop one.

TEXT_COMPARE compares two texts by their bytes under one of the six
relations.

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