Optionally mark pages from cores as de-duplicatable
Linux supports optimistic virtual-memory-level de-duplication for
identical pages. By default, only enable this for compressed cores.
Runtime options --[no-]merge-core-pages can be used to override the
Very much experimental and a hack, but compressed cores would sometimes
be gratuitously inefficient otherwise. If/when support is generalized
to more OSes, figure out how to do this right.