[Node] add StmtsIterable interface to mark nodes that contain iterable stmts to improve hooking in node visitors#836

TomasVotruba wants to merge 3 commits intonikic:masternikic/PHP-Parser:masterfrom

TomasVotruba:tv-stmts-iterableTomasVotruba/PHP-Parser:tv-stmts-iterableCopy head branch name to clipboard