I think we should have something in the manual people can point to
about this, to avoid rehashing it over and over in PRs. "stdenv.lib"
makes it look like lib is part of stdenv, which it isn't, and makes it
even more confusing as a newcomer to figure out what stdenv is (and
isn't).
This is a mostly cosmetical commit, in the sense it doesn't change the contents
of any package, but reorganizes the overall Nixpkgs expressions.
Terminal emulators are an ubiquitous tool for any Unix user; even the beginners
are routinely familiarized to it. And, manifestly, there are many
implementations of terminal emulators out there, from those traditionally made
in C and C++ to those written in Haskell and Go.
Terminal emulators deserve more highlight. This commit does that by creating a
category for them.
