Even if `<datalist>` is dynamically changed, the autocomplete controller still
uses the previous search result. If changed, we have to ignore the previous
result that may now be invalid.
Also, even if `<datalist>` is changed, we have to keep the selected index
(See Mozilla Bug 595069), so we cannot use `ResetInternalState` in this
situation because it resets the selected index.
This resolves#1509.
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.
