FT-594 add fractal tree version 24 (tokudb 7.0.1) and version 27 (tokudb 7.5.0) stress data directories

bits were inconsistent though the handle was opened without those bits
set. This caused dbremove to always fail.

FT-591 fix valgrind uninitialized value error in block allocator test caused by reading past the end of a the blockpair array

FT-273 Prevent setting the memcmp magic on db handles for which a FT is already open. Improve comments. Add a test.

overflow

instead refer to tokuft

one large buffer to serialize a node instead of many smaller ones, which
should hopefully put less pressure on jemalloc during checkpoints etc.

cachefiles, also clean up some formatting.

up report formatting a bit. Also strengthen malformed trace detection.

a running trace (that is, a trace that is still getting written to by some
process)

fragmentation changed

tracing code

ba_replay

create_from_blockpairs would crash the replay. Also fix parsing bugs.

multiple calls), support create_from_blockpairs in the allocator and
trace tool