a vanilla 2-clause BSD license, but somehow some confusing
extra verbage get copied from somewhere.
Also, update the copyright dates to 2007 for all of the files.
Prompted by: several questions about what those extra words really mean
* If write block size is zero, don't block at all.
This supports the unusual requirement of applications
that need "no-delay" writes.
* Expose _write_finish_entry() to give such applications more
control over write boundaries. (Normal applications do not
need this, as entries are completed automatically.)
* Correct the type of write callbacks; this is a minor API
change that does not affect the ABI.
* Correct the error handling in _write_next_header() around
completing the previous entry.
* Correct the documentation for block-size markers: Remove
docs for the long-defunct _read_set_block_size(); document
all of the write block size manipulators.
MFC after: 14 days