changed resolve to map names rather than idents
add hygiene support fns, move them around.

also adds test cases
try removing basically dead code in resolve
resolve test case

resolve must ignore syntax context when comparing module names
flip the switch on let renaming
renaming test cases
comments in ast.rs
removed unneccessary SyntaxExpander structs
separate ItemDecorator from ItemDecorator
refactor so tt_fold only requires an ident->ident fn
adding test case to check marking/unmarking
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added parse_token_trees.rs
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remove FIXME #2888, now bug is fixed
expose top-level mtwt-resolve-crate fn
add call to hygienic resolve