docs: put atomic*.txt and memory-barriers.txt into the core-api book

These files describe part of the core API, but have never been converted to
RST due to ... let's say local oppposition. So, crea

docs: put atomic*.txt and memory-barriers.txt into the core-api book

These files describe part of the core API, but have never been converted to
RST due to ... let's say local oppposition. So, create a set of
special-purpose wrappers to ..include these files into a separate page so
that they can be a part of the htmldocs build. Then link them into the
core-api manual and remove them from the "staging" dumping ground.

Acked-by: Jani Nikula <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
Reviewed-by: David Vernet <[email protected]>
Acked-by: Randy Dunlap <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Corbet <[email protected]>

show more ...