Layout, some final fixes to transition to ll_list.
Implement thread_local keyword fallback.
Fix ll_list release code.
Switch over to static AcqRel.
Use iterator to traverse workqs that want to run.

This means workq don't have to be taken off the runq to determine
if we can run them.  It does make taking them off when they become
empty a little harder though, but that should be offset by there
being less instances of that happening.
Remove debugging code.
Fix pred/succ walk.