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/DIASupport.h

@@ -0,0 +1,33 @@
+//===- DIASupport.h - Common header includes for DIA ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// Common defines and header includes for all LLVMDebugInfoPDBDIA.  The
+// definitions here configure the necessary #defines and include system headers
+// in the proper order for using DIA.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_PDB_DIA_DIASUPPORT_H
+#define LLVM_DEBUGINFO_PDB_DIA_DIASUPPORT_H
+
+// Require at least Vista
+#define NTDDI_VERSION NTDDI_VISTA
+#define _WIN32_WINNT _WIN32_WINNT_VISTA
+#define WINVER _WIN32_WINNT_VISTA
+#ifndef NOMINMAX
+#define NOMINMAX
+#endif
+
+// atlbase.h has to come before windows.h
+#include <atlbase.h>
+#include <windows.h>
+
+// DIA headers must come after windows headers.
+#include <cvconst.h>
+#include <dia2.h>
+
+#endif // LLVM_DEBUGINFO_PDB_DIA_DIASUPPORT_H