Final tweaks for x86 dllimports w/Interlocked functions

git-svn-id: svn://svn.code.sf.net/p/mingw-w64/code/trunk@5968 4407c894-4637-0410-b4f5-ada5f102cad1
winsplp.h: fix PRINTPROVIDOR::fpAddPortEx prototype (r/os svn, r59531)

git-svn-id: svn://svn.code.sf.net/p/mingw-w64/code/trunk@5969 4407c894-4637-0410-b4f5-ada5f102cad1