Squashed 'ext/lltk/' changes from 454ccc4..acfad93

acfad93 add AST.scope for variable scope handling of ast-builder add ast dumper
REVERT: 454ccc4 -n process lasgn add not yet complete tests
REVERT: 2787fb2 -n [lltk] add ast dumper

git-subtree-dir: ext/lltk
git-subtree-split: acfad93d25a45b93c79900f010dcb3b7c9f6bd51
Merge commit '994d9fe5780b1594bd5e261955222e67ff74beac'