C++11 test cleanup: nonthrowing destructors

If a dtor has no interesting members, then it ends up being nothrow,
which affects the generated IR. Modify some tests to tolerate this
difference between C++03 and C++11.

Differential Revision: http://reviews.llvm.org/D27936


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290207 91177308-0d34-0410-b5e6-96231b3b80d8