Preparation for transition of wsd-API-headers to IDL.


git-svn-id: https://svn.code.sf.net/p/mingw-w64/code@6512 4407c894-4637-0410-b4f5-ada5f102cad1
Correct header's dependencies and guards


git-svn-id: https://svn.code.sf.net/p/mingw-w64/code@6513 4407c894-4637-0410-b4f5-ada5f102cad1