BUG: Fix QuadricDecimation on Windows
QuadricDecimation was giving incorrect results on Windows when using Visual Studio 2022 toolset 14.32.31326. This appears to have been a compiler optimizer error. The error only happened on Release mode, not Debug. By using the C++ volatile keyword to inhibit compiler optimizations around the particular incorrectly optimized away variable, the correct result was able to be obtained in Release mode as well.
I believe this will fix the following issues:
- https://discourse.vtk.org/t/vtkquadricdecimation-error-in-vtk9-0/6068
- https://open.cdash.org/test/746295209
Related: !9204 (merged)