swift234

Rework how capture lists work in CaptureExpr: now we record
global variables used by functions in the capture list as well.

SILGen and other things that don't care about these (i.e., all 
current current clients) filter the list to get what they want.

This is needed for future definite init improvements, and unblocked
by Doug's patch in r8039 (thanks! :)

No functionality change.



Swift SVN r8045