This issue is to track the harmonization of duplications in the following core-coder functions: * gain_dec_tc_fx() vs. gain_dec_tc_ivas_fx() * encode_lpc_avq_fx() vs. encode_lpc_avq_ivas_fx() * decode_lpc_avq_fx() vs. decode_lpc_avq_ivas_fx() * lsf_bctcvq_encprm_fx() vs. lsf_bctcvq_encprm_ivas_fx() * lsf_msvq_ma_encprm_fx() vs. lsf_msvq_ma_encprm_ivas_fx() * calc_st_filt_local_fx() vs. calc_st_filt_ivas_fx() * concealment_init_fx() vs. concealment_init_ivas_fx() * Filt_mu_fx() vs. Filt_mu_ivas_fx() <!--- Below are labels that will be added but are not shown in description. This is a template to help fill them. Add further information to the first row and remove and add labels as necessary.-->