Revert "Emit an error when mixing <stdatomic.h> and <atomic>"

It reverts r331378 as it caused test failures

    ThreadSanitizer-x86_64 :: Darwin/gcd-groups-destructor.mm
    ThreadSanitizer-x86_64 :: Darwin/libcxx-shared-ptr-stress.mm
    ThreadSanitizer-x86_64 :: Darwin/xpc-race.mm

Only clang part of the change is reverted, libc++ part remains as is because it
emits error less aggressively.

llvm-svn: 331392
2 files changed
tree: b8cbe5b47a5a14aada05b2115e4bba6e568e8131
  1. clang/
  2. clang-tools-extra/
  3. compiler-rt/
  4. debuginfo-tests/
  5. libclc/
  6. libcxx/
  7. libcxxabi/
  8. libunwind/
  9. lld/
  10. lldb/
  11. llgo/
  12. llvm/
  13. openmp/
  14. parallel-libs/
  15. polly/
  16. README.md
README.md

Low Level Virtual Machine (LLVM)

This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments.