Up to hol.state0

added flatn command in proofManagerLib

in interactive proof, to flatten subgoal stack, so as to merge current list of
subgoals with previous level(s)

expand_list to interactively work on a list of subgoals

also Tactical.VALID_LT, to check that a list-tactical is valid
(expand_list checks validity, expand_listf doesn't)

also abbreviations elt, eall, eta, enth to apply (list-)tactic to subgoal(s)

renaming of functions

Backup -> restore
save_proof -> save

Having two functions "Backup" and "backup" around caused trouble with documentation.

I added another layer of backups / undos to proofManagerLib.

The existing backup-facility records all applications of tactis (by default the last 15 steps) and
the function proofManagerLib.backup allows undoing the last step. This is very useful.
However, it is sometimes useful to be able to got back to user-defined save-points instead of
just auto-recorded last steps.

Therefore, I added two new functions to proofManagerLib (with corresponding ones in Manager and History):

val Backup : unit -> proof
val save_proof : unit -> proof

save_proof allows to store the current status of the proof. All the existing auto-undo history is deleted. So you can't easily go back before that point any more.
You can then continue your proof and use the normal undo as well. At some point, you might want to undo everything up to this save-point.
That's done by Backup. If no save-point has been set, Backup returns to the initial goal, i.e. it behaves like restart.
In constrast to backup, Backup does not delete the save-point by default. So you can go back, re-try the proof from there, and go back again. If you are already
at a save-point (backup fails), then Backup will delete the current save-point and go back to the previous one.

New function "forget_history" added to proofManagerLib. This function can be used during interactive proofs to forbit undos past the current point. Even restarting the proof will return you to the status, when forget_history was executed.

Removed trailing whitespace from all .sml and .sig files.

This affects over 900 files and was done using emacs's delete-trailing-whitespace
function in batch mode. Building the system with Poly/ML and Moscow ML seems to
work, so I'm hoping these changes don't break anything. Please complain if
they do!

Added proofManagerLib. This adds a type of "goal trees"
as an alternative to goalstacks. Relevant entrypoints:

gt ` .... ` -- start a goaltree proof,
analogous to g
eq ` ... ` -- expand a tactic,
analogous to e (except that
the text of the tactic is
delimited by quotes).

A goaltree manages the construction of the final
tactic, so should ease some of the script maintenance
that the goalstack requires.

Backup and restart are just as for goalstacks.

All the entrypoints for goalstacks are just as they
were before; there shouldn't be any difference.