Constrain maximum lifetime of stack closures that capture variables to
be limited by the innermost repeating scope.

Fixes #7336.
auto merge of #7455 : nikomatsakis/rust/issue-7336-constrain-closure-lifetimes, r=pnkfelix

Constrain maximum lifetime of stack closures that capture variables to be limited by the innermost repeating scope.

Fixes #7336.

r? whomever.