synchapi.h: APIs are not forbidden on Windows Store

git-svn-id: svn://svn.code.sf.net/p/mingw-w64/code/trunk@6086 4407c894-4637-0410-b4f5-ada5f102cad1
Add WinRT Windows.Foundation headers

git-svn-id: svn://svn.code.sf.net/p/mingw-w64/code/trunk@6087 4407c894-4637-0410-b4f5-ada5f102cad1
Add WinRT Windows.Security.Cryptography headers

git-svn-id: svn://svn.code.sf.net/p/mingw-w64/code/trunk@6088 4407c894-4637-0410-b4f5-ada5f102cad1
Add WinRT Windows.Storage headers

git-svn-id: svn://svn.code.sf.net/p/mingw-w64/code/trunk@6089 4407c894-4637-0410-b4f5-ada5f102cad1
Add Windows.System.Threading WinRT interfaces

git-svn-id: svn://svn.code.sf.net/p/mingw-w64/code/trunk@6090 4407c894-4637-0410-b4f5-ada5f102cad1