winstorecompat: Fix prototype undefinition for LoadLibraryW

git-svn-id: https://mingw-w64.svn.sourceforge.net/svnroot/mingw-w64@5688 4407c894-4637-0410-b4f5-ada5f102cad1
SetUnhandledExceptionFilter: fix use of InterlockedExchangePointer

git-svn-id: https://mingw-w64.svn.sourceforge.net/svnroot/mingw-w64@5689 4407c894-4637-0410-b4f5-ada5f102cad1
winstorecompat: add VirtualProtect() replacement that just fails

git-svn-id: https://mingw-w64.svn.sourceforge.net/svnroot/mingw-w64@5690 4407c894-4637-0410-b4f5-ada5f102cad1