[coroutines] Add support for coroutines with non-scalar parameters

Summary:
Simple types like int are handled by LLVM Coroutines just fine.
But for non-scalar parameters we need to create copies of those parameters in the coroutine frame and make all uses of those parameters to refer to parameter copies.

Reviewers: rsmith, EricWF, GorNishanov

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D33507

llvm-svn: 303803