Doc: in v12 release notes, explain how to replace uses of consrc and adsrc.
While you can find that info if you drill down far enough, it seems more
helpful to put something right in the compatibility notes. Per a question
from Ivan Sergio Borgonovo.
Discussion: https://postgr.es/m/
a6359855-2a5e-a56c-ebba-
4ea46a1f0ebe@webthatworks.it