Provide DIA implementation of DebugInfoPDB.

This implements DebugInfoPDB when the DIA SDK is present on the system.
Specifically, this means that the following conditions are met:
  1) You are building on Windows.
  2) You are building with MSVC.
  3) Visual Studio did not corrupt the installation of DIA due to a
     known issue with side-by-side installations of VS2012 and VS2013.
If all of these conditions are true, you will be able to pass a value
of PDB_Reader::DIA to PDB::createPdbReader().

There are no tests for this yet, as any test will be in the form of a
lit test which tests the llvm-pdbdump.exe, which still needs to be
rewritten in terms of this library.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228747 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/DebugInfo/PDB/DIA/DIAEnumDebugStreams.h

@@ -0,0 +1,35 @@
+//==- DIAEnumDebugStreams.h - DIA Debug Stream Enumerator impl ---*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_PDB_DIA_DIAENUMDEBUGSTREAMS_H
+#define LLVM_DEBUGINFO_PDB_DIA_DIAENUMDEBUGSTREAMS_H
+
+#include "DIASupport.h"
+#include "llvm/DebugInfo/PDB/IPDBEnumChildren.h"
+
+namespace llvm {
+
+class IPDBDataStream;
+
+class DIAEnumDebugStreams : public IPDBEnumChildren<IPDBDataStream> {
+public:
+  explicit DIAEnumDebugStreams(CComPtr<IDiaEnumDebugStreams> DiaEnumerator);
+
+  uint32_t getChildCount() const override;
+  ChildTypePtr getChildAtIndex(uint32_t Index) const override;
+  ChildTypePtr getNext() override;
+  void reset() override;
+  DIAEnumDebugStreams *clone() const override;
+
+private:
+  CComPtr<IDiaEnumDebugStreams> Enumerator;
+};
+}
+
+#endif