factored out some testing functions to use elsewhere
parser comment
added a hash table to memoize rename and mark operations.

this should make renaming and marking less appallingly slow.
detect unused attrs in one more place, allow parsing to continue for all

changed a bunch of fatal()'s into err()'s, to allow parsing to proceed.
added rename, mark, and resolve fold fns
getting rid of interner_key! macro
starting to add sexp (now rotted, sigh)
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added and rewrote text for 'do' and 'for' loops
working on expand
comments & whitespace
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