Replace OwningPtr<T> with std::unique_ptr<T>.

This compiles with no changes to clang/lld/lldb with MSVC and includes
overloads to various functions which are used by those projects and llvm
which have OwningPtr's as parameters. This should allow out of tree
projects some time to move. There are also no changes to libs/Target,
which should help out of tree targets have time to move, if necessary.

llvm-svn: 203083
diff --git a/llvm/unittests/Support/CompressionTest.cpp b/llvm/unittests/Support/CompressionTest.cpp
index c0a9ada..db6a8bb 100644
--- a/llvm/unittests/Support/CompressionTest.cpp
+++ b/llvm/unittests/Support/CompressionTest.cpp
@@ -12,7 +12,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/Compression.h"
-#include "llvm/ADT/OwningPtr.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Config/config.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -25,8 +24,8 @@
 #if LLVM_ENABLE_ZLIB == 1 && HAVE_LIBZ
 
 void TestZlibCompression(StringRef Input, zlib::CompressionLevel Level) {
-  OwningPtr<MemoryBuffer> Compressed;
-  OwningPtr<MemoryBuffer> Uncompressed;
+  std::unique_ptr<MemoryBuffer> Compressed;
+  std::unique_ptr<MemoryBuffer> Uncompressed;
   EXPECT_EQ(zlib::StatusOK, zlib::compress(Input, Compressed, Level));
   // Check that uncompressed buffer is the same as original.
   EXPECT_EQ(zlib::StatusOK, zlib::uncompress(Compressed->getBuffer(),