Add missing includes.

[v.g.vassilev]

Summary

I am not sure if we should #include <atomic> but the instantiation of operator* of ManagedStatic needs std::memory_order_aquire. Modules builds error out with:

`In module 'LLVM_Utils' imported from /home/vvassilev/workspace/llvm-git/src/lib/Support/CommandLine.cpp:19:
/home/vvassilev/workspace/llvm-git/src/include/llvm/Support/ManagedStatic.h:66:26: error:

  definition of 'memory_order' must be imported from module
  'LLVM_Utils.ADT.IntrusiveRefCntPtr' before it is required
void *Tmp = Ptr.load(std::memory_order_acquire);
                     ^

/home/vvassilev/workspace/llvm-git/src/include/llvm/Support/ManagedStatic.h:73:29: note:

    in instantiation of member function 'llvm::ManagedStatic<(anonymous
    namespace)::CommandLineParser>::operator*' requested here
C *operator->() { return &**this; }
                          ^

/home/vvassilev/workspace/llvm-git/src/lib/Support/CommandLine.cpp:339:15: note:

    in instantiation of member function 'llvm::ManagedStatic<(anonymous
    namespace)::CommandLineParser>::operator->' requested here
GlobalParser->addLiteralOption(O, Name);
            ^

/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/bits/atomic_base.h:56:16: note:

    previous definition is here
typedef enum memory_order
             ^

1 error generated.
`

[rsmith]

ManagedStatic.h already includes <atomic>, so the additional includes of <atomic> don't seem appropriate to me. Looks like this may have hit a bug in enum merging?

[v.g.vassilev]

The 'atomic' bug was fixed I assume as part of https://llvm.org/bugs/show_bug.cgi?id=28794

Other includes landed in r281450.

lib/Support/APInt.cpp

 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
+#include <climits>
 #include <cmath>
 #include <cstdlib>
 #include <cstring>
-#include <limits>
 using namespace llvm;
 
 #define DEBUG_TYPE "apint"

lib/Support/CachePruning.cpp

 #define DEBUG_TYPE "cache-pruning"
 
 #include <set>
+#include <system_error>
 
 using namespace llvm;
 

lib/Support/CommandLine.cpp

 #include "llvm/Support/Path.h"
 #include "llvm/Support/StringSaver.h"
 #include "llvm/Support/raw_ostream.h"
+#include <atomic>
 #include <cstdlib>
 #include <map>
 using namespace llvm;

lib/Support/CrashRecoveryContext.cpp

 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Mutex.h"
 #include "llvm/Support/ThreadLocal.h"
+#include <atomic>
 #include <setjmp.h>
 using namespace llvm;
 

lib/Support/Debug.cpp

 #include "llvm/Support/Signals.h"
 #include "llvm/Support/circular_raw_ostream.h"
 #include "llvm/Support/raw_ostream.h"
+#include <atomic>
 
 #undef isCurrentDebugType
 #undef setCurrentDebugType

lib/Support/DeltaAlgorithm.cpp

 #include "llvm/ADT/DeltaAlgorithm.h"
 #include <algorithm>
 #include <iterator>
+#include <set>
 using namespace llvm;
 
 DeltaAlgorithm::~DeltaAlgorithm() {

lib/Support/Error.cpp

 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/ManagedStatic.h"
-
+#include <atomic>
+#include <system_error>
 
 using namespace llvm;
 

lib/Support/ErrorHandling.cpp

 #include "llvm/Support/Threading.h"
 #include "llvm/Support/WindowsError.h"
 #include "llvm/Support/raw_ostream.h"
+#include <atomic>
 #include <cassert>
 #include <cstdlib>
 

lib/Support/LockFileManager.cpp

 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/Signals.h"
+#include <atomic>
+#include <system_error>
 #include <sys/stat.h>
 #include <sys/types.h>
 #if LLVM_ON_WIN32

lib/Support/ManagedStatic.cpp

 #include "llvm/Support/Mutex.h"
 #include "llvm/Support/MutexGuard.h"
 #include "llvm/Support/Threading.h"
+#include <atomic>
 #include <cassert>
 using namespace llvm;