Check in test that demonstrates ABI break for std::function.

Our C++03 and C++11 implementations of function are not ABI
compatible. I've added a "test" that demonstrates this.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@363092 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed