Add new make targets world-bin and install-world-bin
These are the same as world and install-world respectively, but without
building or installing the documentation. There are many reasons for
wanting to be able to do this, including speed, lack of documentation
building tools, and wanting to build other formats of the documentation.
Plans for simplifying the buildfarm client code include using these
targets.
Backpatch to all live branches.
Discussion: https://postgr.es/m/
6a421136-d462-b043-a8eb-
e75b2861f3df@dunslane.net