Add Open Packaging Convention-compliant files API added with Windows 7


git-svn-id: https://svn.code.sf.net/p/mingw-w64/code@6526 4407c894-4637-0410-b4f5-ada5f102cad1
Add first of five parts to add XPS-support


git-svn-id: https://svn.code.sf.net/p/mingw-w64/code@6527 4407c894-4637-0410-b4f5-ada5f102cad1