Correct return-value for sqrt (-0.0) case as -0.0 as decribed in C99
(cherry picked from commit d734ba54a365c1e8da814184aa4d1eed7e869665)
include pshpack1.h and poppack.h before and after the structure typedefs (bug #419)
dwmapi.h: Removed version guard

git-svn-id: svn+ssh://svn.code.sf.net/p/mingw-w64/code/trunk@5110 4407c894-4637-0410-b4f5-ada5f102cad1