This is needed if we compile StdlibUnittest with -sil-serialize-all
So far I added the imports only in files which needed them. But this may change, depending on the optimizer (inlining).
Adding them in all files doesn't harm and avoids confusion if someone makes an unrelated change which would result in such a linker error.
Some of the tests had bitrotted, and others no longer worked
because they used frameworks such as CoreAudio that are not
available in the public SDK for watchOS.
Swift SVN r32733
<rdar://problem/20855539> Add SCNVector3/4 Swift convenience
<rdar://problem/20854576> Add SCNFloat to the SceneKit swift overlay
Patch by Amaury Balliet.
Swift SVN r30353
