Enables the touching of all memory pages used by the JVM heap spaces
during initialization of the HotSpot VM, which commits all memory pages
at initialization time. By default, pages are committed only as they are
needed.
ba5be0332d removed support for degrading
to slf4j and j.u.l but didn't document this as a breaking change because
it is only breaking for folks using Elasticsearch's jar as a java client.
People do that so this counts as a breaking change.
Also, if anyone was brave enough to try and replace log4j on an installed
version of Elasticsearch that will no longer work and this documents that
as well. It doens't get a full heading and instead lives with the java
client notes. Mostly because I can't imagine it worked consistently enough
for anyone to actually do it in the first place. We just never tested it
well enough to make sure we didn't break it after it was implemented.