Squashed commit of the following:
commit 23c5f1d3f9b13ff9e46ce3de96aefeb655d5ed97
Author: John Wellbelove <github@wellbelove.co.uk>
Date: Sun Jan 31 12:32:35 2021 +0000
Fixed rollover error for etl::queue_spsc_atomic
Added 'required_alignment' parameter to 'allocate' for etl::imemeory_block_allocator.
Updated QueuedMessageRouter example
