- Rework the underlying ALQ storage to be a circular buffer, which amongst other
things allows variable length messages to be easily supported.
- Extend KPI with alq_writen() and alq_getn() to support variable length
messages, which is enabled at ALQ creation time depending on the
arguments passed to alq_open(). Also add variants of alq_open() and
alq_post() that accept a flags argument. The KPI is still fully
backwards compatible and shouldn't require any change in ALQ consumers
unless they wish to utilise the new features.
- Introduce the ALQ_NOACTIVATE and ALQ_ORDERED flags to allow ALQ consumers
to have more control over IO scheduling and resource acquisition
respectively.