Fix “stop” reactivity

Destroy members of a DOMRange immediately on invalidation of the last render, not waiting for re-run.  Provide DOMRange#destroyMembers.

Don’t call view.autorun from view.render() in builtins, and enforce it.

Remove dead code “onstop” from DOMRange.
Fix rest of the render tests
Fix UI.contentBlock data context
Fix scanner_tests
Fix compile_tests
Cleaner codegen of attribute values
Fix remaining tests (less and stylus)