Make two vtable tests tolerate C++11.

In C++11 we don't emit vtables as eagerly as we do for C++03, so
fiddle the tests to emit them when the test expects them.

Differential Revision: http://reviews.llvm.org/D27994


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290205 91177308-0d34-0410-b5e6-96231b3b80d8