BUG: 5445: tweaks to get 1.2.3 working with shared libs

Utilities/vtkzlib/README.Kitware.txt

@@ -35,4 +35,5 @@ vs the original zlib code
 
 zconf.h
   -Include vtk_zlib_mangle.h (at the top)
+  -Include vtkzlib/zlibDllConfig.h (at the top)
   -Suppress selected compiler warnings (at the bottom)

Utilities/vtkzlib/zconf.h

@@ -11,6 +11,9 @@
 /* KITWARE_ZLIB_CHANGE - Added to mangle function names */
 #include "vtk_zlib_mangle.h"
 
+/* KITWARE_ZLIB_CHANGE - Added to get the correct definition of ZLIB_DLL */
+#include "vtkzlib/zlibDllConfig.h"
+
 /*
  * If you *really* need a unique prefix for all types and library functions,
  * compile with -DZ_PREFIX. The "standard" zlib should be compiled without it.