This was not likely an error-free change. Where you see problems
please correct them. This went through a fairly tedious audit
before committing, but comments might have been changed incorrectly,
not changed at all, etc.
Swift SVN r7631
I actually backtracked on the name and went back to [backref].
The main changes here are (1) [backref] is now definitively a
decl attribute and (2) there's now a huge new section about
closures. This entailed doing quite a bit of secondary design
on closure capture semantics because backref captures are
value captures, and adding those just does so much fun stuff
to the model.
Swift SVN r5836
