HAMMER 24B/many: Edge cases, cleanups
* Use create_tid instead of delete_tid in B-Tree key comparisons. I
actually used create_tid's originally, then switched to delete_tid's
because historical searches could iterate forwards to locate
matching records whereas using create_tid required a backwards
iteration.
However, because delete_tid's can be modified in-place (0 -> delete stamp),
this introduced some rare edges cases that I had not considered.
So go back to using create_tid's. The iteration code actually just does
a re-search now with a slightly different key, so no new code had
to be written for the reverse-direction. Create TIDs do not change once
they are laid down so there are no additional cases to consider.
* Fix a missing create_tid initialization in hammer_object.c.