Adjust Cubic Hermite's BC parameters to the correct values.

[Isaac]

Currently, Hermite BC values are B=0.5, C=0.5 when both should be B=0, C=0.

Link to filter function.

Reference:
Imagemagick Cubic B,C Expert Controls

[wiwaz]

In addition to the b/c values, the filter radius is 2.0, but Hermite only has a single positive lobe.

[Isaac]

The filter has a merge request, closing the issue now.