Is `ITK_USE_FLOAT_SPACE_PRECISION` obsolete? Build errors when = YES.

I've been building ITK with various build option permutations (to try and shake out the last -Wextra-semi warnings) and it seems to me that ITK does not build with `ITK_USE_FLOAT_SPACE_PRECISION = YES`.

ex:

```
Modules/Core/ImageFunction/test/itkVectorInterpolateImageFunctionTest.cxx:223:14: error: no matching conversion for functional-style cast from 'itk::SpacePrecisionType[3]' (aka 'float[3]') to 'ContinuousIndexType' (aka 'ContinuousIndex')
cindex = ContinuousIndexType(darray);
^~~~~~~~~~~~~~~~~~~~~~~~~~
```

and

```
Modules/Filtering/ImageGrid/test/itkBinShrinkImageFilterTest2.cxx:45:12: error: no matching function for call to 'FloatAlmostEqual'
if (!itk::Math::FloatAlmostEqual(pt[i], it.Get()[i]))
^~~~~~~~~~~~~~~~~~~~~~~~~~~
```

and others too.

Seems like no one is using this if it doesn't even build?