[AD] uthreads.c revisited

[Chris <kcat@xxxxxxxxxx>]

I'm just going through this in my head... in the threaded background 
process manager for input and sound, we have this:

      /* run the callbacks for each 10ms elapsed, but limit to 18ms */
      if (interval > 18000)
         interval = 18000;
      while (interval > 10000) {

However, I think I may have an issue or two with it. First off, I 
understand that the interval is clamped to 18ms so it doesn't run away 
due to a cpu spike or process pause or something. But, I'd want to ask 
if clamping is necessary? And if it is, I think it should be changed to 
something like this:

      if (interval > 20000)
         interval = 20000;
      while (interval >= 10000) {
or
      if (interval > 18000)
         interval = 18000;
      if (interval >= 10000) {

In both cases, the bg processes run when the interval is >= 10ms, 
instead of only > 10ms. For the first, it increases the max clamp value 
to 20ms, so the while loop would run twice if it was that far behind 
(this could be what the original clamp was aiming for but due to 
MAX_INT, couldn't get higher than 17.99ms). For the second, it changes 
the while to an if, since even if interval was 20ms or more, it would've 
been clamped to 18ms and the while loop would only run once anyway 
(granted optimizations would clear this out, but it doesn't look very 
clean).

- Kitty Cat