Add end-to-end tests for overflows of byval arguments.

Summary:
Included is one test for passing structs by value and one test for passing C++
objects by value.

Submitted on behalf of Matt Morehouse.

Reviewers: eugenis, vitalybuka

Reviewed By: eugenis

Subscribers: srhines, kubamracek, llvm-commits

Differential Revision: https://reviews.llvm.org/D34827

llvm-svn: 308677