Support C++11 in folly/IPAddress.h w.r.t. aligned_union
Support C++11 in folly/IPAddress.h w.r.t. aligned_union

Summary: [Folly] Support C++11 in `folly/IPAddress.h` w.r.t. `aligned_union` by avoiding `aligned_union_t`, which is C++14.

Reviewed By: spalamarchuk, mengz0

Differential Revision: D14278604

fbshipit-source-id: 474ac0aa0110f4939d1042d334b69feb6b2644cb

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly