Hello,

I just finished merging HEAD into the branch implementing constraint solver plugins (`wip/tc-plugins`), so things should be fully up to date.  For ease of review, I squashed everything into a single commit:

could interested folks (I know of SimonPJ, Richard, and Adam) have a look and let me know if things look reasonable?

On a related note:  I know that we are using phabricator for code review, but I don't know how to use it yet, so please let me know if I can do something to make the review easier.

-Iavor