Fix defaulted-functions-in-C++98 extension to give the functions the same

effect they would have in C++11. In particular, they do not prevent
value-initialization from performing zero-initialization, nor do they prevent a
struct from being an aggregate.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290229 91177308-0d34-0410-b5e6-96231b3b80d8