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

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Merge pull request #2618 from csware/msvc-no-z-prefix

There is no "z" size specifier on MSVC