An xref to a <para>'s ID isn't very helpful because paras don't have
names. This causes a warning while building PDFs, though for some
reason not while building HTML. The link arguably went to the wrong
place, too.
To fix, introduce a sub-section we can reference.
As promised in earlier commits, this adds documentation about the new
build options, the new GUCs, about the planner logic when JIT is used,
and the benefits of JIT in general.
Also adds a more implementation oriented README.
I'm sure we're going to want to expand this further, but I think this
is a reasonable start.
Author: Andres Freund, with contributions by Thomas Munro
Reviewed-By: Thomas Munro
Discussion: https://postgr.es/m/20170901064131.tazjxwus3k2w3ybh@alap3.anarazel.de