__init__(): FullLog must now maintain a list of created versions so
that the Berkeley storage can query it when it's got a version string
it doesn't know about.  Otherwise, we'll just create multiple
create-version entries in the log.

finish(): clear the __versions dict.

get_vid(): Look up a version string, returning the associated vid, or
None (by default).

write_object(), write_nonversion_object(), write_moved_object,
write_new_version, write_discard_version(): Higher level interface to
adding new commit log entries.  There's really only three record
types, but it helps to have the higher level API.

next_object(): Get the next entry in the commit log, but assert that
the key is one of `o', `v', or `d'.

Also, fix a typo and get rid of the old store() and storeNV() methods.

epilogue and initial and final events.  (This is not used anywhere but
I thought it was neat, and it matches what I did in
test_htmltalparser.py.)

spurious log entry about unindexing a non-existent object.

which generated spurious log entry about unindexing a non-existent
object.

    - make function decls prototypes
    - remove unreferenced functions

XXX should remove Xaq eventually

checkin to this file.  For <br>, we now end up calling
emitEndElement() with isend = 1 and implied = -1, so it doesn't emit
</br> text, but properly pops the todo stack.

other versions of expat that might pop up elsewhere.

Eventually, this version needs to go away.

end.  This would have caught the problem exposed in test10.html
earlier.

To prevent this in the future, read the path from a file .path.