datastruct/atom.h: Fix documentation for atom_for_block: ATOM_NOT_FOUND -> atom_NOT_FOUND.
datastruct/vector: The struct tag ought to be 'vector', not 'vector_t'.
datastruct/vector/set-width.c: Fix vector_set_width squeezing the block /after/ its containing block had been resized.
databases/pickle: Convert pickle and unpickle to use C standard IO.
Add DPTLibTest.

* Add new test shell main.c.
* Add return codes for test pass/fail.
* Amend test routines to use it.
* Amend test routines to goto common Failure blocks.
* Fix digest buffers needing unsigned chars in tag-db-test.
datastruct/hash/walk-cont.c: hash_walk_continuation: Don't walk off end of bins array when scanning for continuation start.
databases/digest-db/digest-db.c: hash_walk_continuation: Avoid non-idiomatic loops.