A user reported an issue with bumping into the chain limits in 0.12 on IRC this evening, and I realized that we don't seem to mention these new policy limits in the release notes.
I wasn't sure exactly what to say here, as we apparently decided to hide the command line options for changing these values as a help-debug option, and even phrasing the exact limits is a bit tedious and technical, so I figured I'd just highlight the main idea of the limits and not explain exactly how they're implemented or how exactly you'd change them (ie with separate ancestor and descendant limits).
