Bug#976977: vtk6 FTBFS with freetype 2.10.4

[Adrian Bunk]

Source: vtk6
Version: 6.3.0+dfsg2-6
Severity: serious
Tags: ftbfs

https://buildd.debian.org/status/package.php?p=vtk6

...
/<<PKGBUILDDIR>>/Rendering/FreeType/vtkFreeTypeUtilities.cxx:336:1: error: expected constructor, destructor, or type conversion before ‘vtkFreeTypeUtilitiesFaceRequester’
  336 | vtkFreeTypeUtilitiesFaceRequester(FTC_FaceID face_id,
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/<<PKGBUILDDIR>>/Rendering/FreeType/vtkFreeTypeUtilities.cxx: In member function ‘void vtkFreeTypeUtilities::InitializeCacheManager()’:
/<<PKGBUILDDIR>>/Rendering/FreeType/vtkFreeTypeUtilities.cxx:484:27: error: ‘vtkFreeTypeUtilitiesFaceRequester’ was not declared in this scope; did you mean ‘vtkFreeTypeUtilitiesCleanup’?
  484 |                           vtkFreeTypeUtilitiesFaceRequester,
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                           vtkFreeTypeUtilitiesCleanup
...