Fix #285: alf_luma/chroma_coeff_delta_sign interpretation
According to specification, alf_luma_coeff_delta_sign = 1 means that filtCoeff is negative. Idem with alf_chroma_coeff_delta_sign and AlfCoeffC.
Edited by Remy Foray
According to specification, alf_luma_coeff_delta_sign = 1 means that filtCoeff is negative. Idem with alf_chroma_coeff_delta_sign and AlfCoeffC.