lavfi: add haldclutsrc filter.
lavfi: add dual input helpers.
lavfi: add haldclut filter.

Fixes Ticket #2517.
lavfi/lut3d: move lut3d init to its definition scope.
lavfi/overlay: remove do_blend forward declaration.
lavfi/haldclutsrc: 10l remove size options.
j2k/jpeg2000: merge j2k & jpeg2000 dwts, drop j2k dwt

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>