initial custom action library, "hello, world" quality

src/installer-ca/dutil/fileutil.h

+#pragma once
+//-------------------------------------------------------------------------------------------------
+// <copyright file="fileutil.h" company="Outercurve Foundation">
+//   Copyright (c) 2004, Outercurve Foundation.
+//   This software is released under Microsoft Reciprocal License (MS-RL).
+//   The license and further copyright text can be found in the file
+//   LICENSE.TXT at the root directory of the distribution.
+// </copyright>
+// 
+// <summary>
+//    Header for file helper functions.
+// </summary>
+//-------------------------------------------------------------------------------------------------
+
+extern "C" {
+
+#define ReleaseFile(h) if (INVALID_HANDLE_VALUE != h) { ::CloseHandle(h); h = INVALID_HANDLE_VALUE; }
+#define ReleaseFileHandle(h) if (INVALID_HANDLE_VALUE != h) { ::CloseHandle(h); h = INVALID_HANDLE_VALUE; }
+#define ReleaseFileFindHandle(h) if (INVALID_HANDLE_VALUE != h) { ::FindClose(h); h = INVALID_HANDLE_VALUE; }
+
+HRESULT DAPI FileVersion(
+    __in_z LPCWSTR wzFilename, 
+    __out DWORD *pdwVerMajor, 
+    __out DWORD* pdwVerMinor
+    );
+}