MemLog.v: prove TBegin (and thus all of tp_atomicity)
MemLog.v: prove TBegin (and thus all of tp_atomicity)

uses the same set of still-unproved lemmas about pflush

mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl