There is no "z" size specifier on MSVC

See http://msdn.microsoft.com/en-us/library/tcxf1dw6.aspx and https://stackoverflow.com/questions/6655410/why-doesnt-zd-printf-format-work-in-vs2010
I'm unsure about `|| defined(__MINGW32__)`, maybe `defined(WIN32)` would be the option to go?!