swift234

Clone partially applied functions in an effort to eliminate more boxes.

Attempt to promote boxes to stack allocations by examining partial_apply
instructions that the boxes appear as arguments in, and then if things
look good examining the apply that the partial_apply is passed to in
order to ensure the partial_apply is not captured. If it looks like we
can legally promote the box, clone the partially applied function to
remove the box container pointer, and rewrite the partial_apply.

Fixes <rdar://problem/16373639>.

Swift SVN r15727