Patch to allow compilation on Visual Studio 2008.
Versions of Visual Studio prior to 2005 did not have vsnprintf, so there was a line in zutil.h:
# define vsnprintf _vsnprintf
that was conditionally compiled in. This is not only not needed in Visual Studio 2008, but prevents U3D from compiling.
The fix is to add another condition to the compilation, so the #define is only included if this is not Visual Studio, or the version of Visual Studio is before VS 2005.