update for rename of dropWhile_DEF
add mlstring_case syntax fns
another nub_DEF rename
Added partial (only for ASTs) impl for #3
removed last cheat from translator (DeclAssumCons)

Commit includes definition and lemmas about ASHADOW,
which removes shadow entries from an a-list. This should
eventually be moved into HOL's alistTheory.
implementing new-ref, wip
some work on bvi_to_bvp
more progress on bvi_To_bvp
some fixes to x64_heap
minor progress on x64
a bit of progress on bvi-to-bvp compiler proof
bit more progress on bvi-to-bvp proof
bvi-to-bvp proof cheat free!
Ref part of zBC_HEAP_THM proved
uncommented zBC_HEAP_INIT, works again
real_inst_length updated, cheat removed
fixed proof borken by change to real_inst_length
progress with removing code_length cheat
progress on code-heap-limit test
progress with code-heap-length cheat