Microtasks, resolved Promises and Observers are handled after the sync
task that caused them, in the order they were generated.
Also simplifies reentrancy handling.
Based-on: m-c 1193394
Since these are just interpreted comments, there's 0 impact on actual code.
This removes all lines that match /* vim: set(.*)tw=80: */ with S&R -- there are
a few others scattered around which will be removed manually in a second part.
