ml_heap partly updated for wide refs
progress on ml_heap for wide refs
more progress on wide refs
more progress on ml_heap with wide refs
wide refs, deref case verified
new wide ref verified
reorganise proofs about hol's consistency

the proofs about the context extension rules are really more like
soundness rules; now they are in their own theory.

also, make a promise in the README (not yet fulfilled) to prove
HOL-without-infinity consistent (because this should be doable without
assumptions).

would also like to reduce the is_set_theory and is_infinite assumptions
to a single, self-contained, plausible-looking large-cardinal axiom.
Add type abbreviations to the concrete syntax.

Next step will be to parse them (i.e., parsing completeness will fail
at the moment).
Refine PEG to handle type abbreviations

Prove soundness, completeness, and that ptree conversion is total.

Note in passing that semantics/cmlPtreeConversion is not converting a
parse-tree corresponding to the "bool" type-operator to TC_bool, but
rather to

   TC_name (Short "bool")

Also, the list of possible tctors is missing TC_list.
x64_heap builds again
Merge branch 'x64-wip'
attempt to use translator's equality type theorems to prove some cheats

but the translator does not produce enough such theorems, so no cheats
proved yet.
prove that hol-minus-infinity has a model

(without the set-theoretic infinity axiom as an assumption)
add back missing opening comment to x64_heapScript.sml

hopefully put it in the right place...
fix some references since theorems have moved

I think I did this already somewhere but maybe it got lost in a merge.
Parse type abbreviations in signatures.

(Some other updates to grammar.txt made as well, to try to bring it
into line with what's in gramScript.)
Partial changes to explorer
Removed elab step and changed some decls in compute_bytecodeLib
Explorer builds with some code copied from standalone
Fixed bc_inst in astPP