Overhaul error handling in the core framework

[fgvanzee]

Going forward, this PR branch will implement the changes set forth in #479.

To start out with, only the new configure options are implemented. I'll incrementally update parts of the framework to (a) observe the new error checking flags and respond accordingly, and (b) return err_t values up the call stack wherever possible.

Thanks for your patience on this project, @jdiamondGitHub.