[isabelle-dev] NEWS: better resource usage on all platforms

[Makarius]

This refers to the NEWS update in adcaaf6c9910.

In the past few months there have been many changes on both the ML and 
Scala side to make more of available resources, and to avoid demanding too 
much of them.  In the coming weeks it is important to keep a keen eye on 
how it works in practice.


The latest and cheapest trick is

changeset:   62115:57895801cb57
user:        wenzelm
date:        Sun Jan 10 23:25:11 2016 +0100
files:       etc/options src/Pure/PIDE/session.scala
description:
prune old versions more often, to reduce overall heap requirements;


Users with a private editor_prune_delay in etc/preferences should follow 
that change.


 	Makarius