VTK Writer: Fixed double use of SegmentHandleType, which caused GCC 4.2 to break.

The following is a bug in GCC 4.2 (and bad style anyway):
 class T
 {
   typedef SomeType    SegmentHandleType;

   template <SegmentHandleType>
   void foo(SegmentHandleType const & bar) { /* use SegmentHandleType here */ }
 };

 T t;
 t.foo(SomeOtherType());

because G++ 4.2 will then use 'SomeType' in the body of foo().
Anyway, if we had applied the coding style guide rigorosly, this problem would have never shown up :-(