Revert "[libcxx] implement <experimental/simd> declarations based on P0214R7."

This reverts commit r330627.

This causes several bots to freak out.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@330636 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/experimental/simd/simd.casts/simd_cast.pass.cpp

@@ -1,40 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++98, c++03
-
-// <experimental/simd>
-//
-// [simd.casts]
-// template <class T, class U, class Abi> see below simd_cast(const simd<U, Abi>&);
-#include <experimental/simd>
-#include <cstdint>
-
-using namespace std::experimental::parallelism_v2;
-
-static_assert(std::is_same<decltype(simd_cast<int32_t>(native_simd<int32_t>())),
-                           native_simd<int32_t>>::value,
-              "");
-
-static_assert(
-    std::is_same<decltype(simd_cast<int64_t>(fixed_size_simd<int32_t, 4>())),
-                 fixed_size_simd<int64_t, 4>>::value,
-    "");
-
-static_assert(std::is_same<decltype(simd_cast<fixed_size_simd<int64_t, 1>>(
-                               simd<int32_t, simd_abi::scalar>())),
-                           fixed_size_simd<int64_t, 1>>::value,
-              "");
-
-static_assert(std::is_same<decltype(simd_cast<simd<int64_t, simd_abi::scalar>>(
-                               fixed_size_simd<int32_t, 1>())),
-                           simd<int64_t, simd_abi::scalar>>::value,
-              "");
-
-int main() {}