[vtkusers] VTK Utility Library Mangling

[Brad King]

Hello,

The zlib, png, jpeg, tiff, and expat libraries in the VTK/Utilities 
directory now have all symbols mangled to begin with a vtk_ prefix. 
This will avoid conflicts when applications try to link against vtkIO 
and a system version of one of these libraries.

For some reason, Visual Studio .NET does not recognize that the header 
files for some of these libraries have changed and do not rebuild the 
.dll files for them.  If you get unresolved symbol errors for one of 
these libraries, just right-click on the library in the GUI and select 
"rebuild".  Then try your build again.

-Brad