parser: index_hint_list -> IndexHints
parser: drop obsolete tokens
parser VALUES -> Values
parser: group_by_opt -> GroupBy
parser: having_opt -> Where
parser: order_by_opt -> OrderBy
parser: limit_opt -> Limit
parser: bunch of misc non-terminals converted
parser: update_list -> UpdateExprs
parser: case_expression -> CaseExpr

As of this CL, newast.go has no reference to Node.
Now the next phase of cleanup begins, with the tokenizer,
followed by fine-tuning of the grammar and AST.
Merge branch 'master' into parser