queue: warn if high watermark is set too low
queue: auto-adjust watermarks
bugfix: legacy directive $ActionQueueWorkerThreads was not honored
queue.workerThreadMinimumMessage set to queue.size / num workers
bugfix: legacy directive $ActionQueueWorkerThreads was not honored

Conflicts:

	ChangeLog
	runtime/queue.c
Merge branch 'v7-stable' into v7-devel
Merge branch 'v7-devel'
doc: maintain ChangeLog