Add "INSTALLED" pseudo package to refer to all installed packages
Review Request #127185 - Created Feb. 25, 2016 and updated
Summary says about all, really, and the diff itself is very small. My use-case is
emerge --cleanbuild INSTALLED
to clean all build directories. I suppose it could potentially also be useful for some other actions that don't have an "--XYall"-variant, yet.
Ran it, and had a handful GB more free disk space, afterwards.