update SyntaxNode#initialize to force creation of parent links
work on detecting branching into / out of parallel loops
update TODO
prevent derived-type items from being recognized as serial 'vars in region'
use 'e' alias; add Xinput#to_s
more work on detecting branching into / out of parallel loops
update TODO
mv lib -> treetop
rm old treetop
update treetop & polyglot
mv treetop -> lib