Revert r283680.

Breaks bootstrap builds on (at least) Windows:
In file included from D:\buildslave\clang-x64-ninja-win7\llvm\lib\Support\Allocator.cpp:14:
In file included from D:\buildslave\clang-x64-ninja-win7\llvm\include\llvm/Support/Allocator.h:24:
In file included from D:\buildslave\clang-x64-ninja-win7\llvm\include\llvm/ADT/SmallVector.h:20:
In file included from D:\buildslave\clang-x64-ninja-win7\llvm\include\llvm/Support/MathExtras.h:19:
D:\buildslave\clang-x64-ninja-win7\stage1.install\bin\..\lib\clang\4.0.0\include\algorithm(63,8) :
    error: unknown type name '__device__'
    inline __device__ const __T &


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@283747 91177308-0d34-0410-b5e6-96231b3b80d8