swift234

Compute captures after all bodies have been type-checked, as a separate pass.

We already have the restriction that captures can't be computed until
everything is type-checked, but previously we tried to compute captures
/immediately/ after a closure was type-checked. Unfortunately, we either
type-checked too early (before @noescape was propagated onto multi-statement
closures) or too late (trying to compute autoclosure captures at the point
the autoclosure was introduced).

Now, all closure captures are computed after type-checking, and local
function captures as well. They also more consistently reuse the capture
list of nested closures/functions. Because captures can be computed on
demand, there is now a flag on CaptureInfo for whether we've computed
captures yet. Note that some functions will never have captures computed,
namely those that are not in a local context.

rdar://problem/19956242

Swift SVN r25776