MemLog.v: prove [apply_ok]
MemLog.v: prove [apply_ok]

No admit left in MemLog.v.  But need to fix some broken proofs.

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